Java : Files 示例

Files (Java SE 22 & JDK 22) 示例。
您将在大多数 Files 方法中找到代码示例。

注解 :

本文可能使用了翻译软件以方便阅读。另请查看英文原文。

简介

此类仅由对文件、目录或其他类型文件进行操作的静态方法组成。 (机器翻译)

Class diagram

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt
System.out.println(Files.notExists(path)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

Files.writeString(path, "abcd");

System.out.println(Files.exists(path)); // true
System.out.println(Files.readString(path)); // abcd

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode                 LastWriteTime         Length Name
//----                 -------------         ------ ----
//-a---          2024/10/19    15:48              4 aaa.txt

Files.delete(path);
System.out.println(Files.notExists(path)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

Annotation :

Most of the code examples in this article are run on Windows.
Some of the code examples are run on Linux for POSIX.

Methods

static long copy (InputStream in, Path target, CopyOption... options)

将输入流中的所有字节复制到文件。 (机器翻译)

final var source = Path.of("D:", "java-work", "source.txt");
System.out.println(source); // D:\java-work\source.txt

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

Files.writeString(source, "abcd");
System.out.println(Files.exists(source)); // true
System.out.println(Files.exists(target)); // false

// --- PowerShell ---
//PS D:\java-work> ls -Name
//source.txt

try (final var in = Files.newInputStream(source)) {
    final var ret = Files.copy(in, target);
    System.out.println(ret); // 4
}

final var str = Files.readString(target);
System.out.println(str); // abcd

// --- PowerShell ---
//PS D:\java-work> ls -Name
//source.txt
//target.txt

final var url = URI.create("https://example.com").toURL();
System.out.println(url); // https://example.com

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt
System.out.println(Files.notExists(target)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

try (final var in = url.openStream()) {
    final var ret = Files.copy(in, target);
    System.out.println(ret); // 1256
}

final var str = Files.readString(target);
System.out.println(str);

// Result
// ↓
//<!doctype html>
//<html>
//<head>
//    <title>Example Domain</title>
//...

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

Files.createFile(target);
System.out.println(Files.exists(target)); // true

// --- PowerShell ---
//PS D:\java-work> ls -Name
//target.txt

final byte[] buf = {10, 20, 30};

try (final var in = new ByteArrayInputStream(buf)) {
    Files.copy(in, target);
} catch (FileAlreadyExistsException e) {
    System.out.println("FileAlreadyExistsException!");
}

// Result
// ↓
//FileAlreadyExistsException!

try (final var in = new ByteArrayInputStream(buf)) {
    Files.copy(in, target, StandardCopyOption.REPLACE_EXISTING);
    System.out.println(Arrays.toString(Files.readAllBytes(target)));
}

// Result
// ↓
//[10, 20, 30]

static long copy (Path source, OutputStream out)

将文件中的所有字节复制到输出流。 (机器翻译)

final var source = Path.of("D:", "java-work", "source.txt");
System.out.println(source); // D:\java-work\source.txt

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

Files.writeString(source, "abcd");
System.out.println(Files.exists(source)); // true
System.out.println(Files.exists(target)); // false

// --- PowerShell ---
//PS D:\java-work> ls -Name
//source.txt

try (final var out = Files.newOutputStream(target)) {
    final var ret = Files.copy(source, out);
    System.out.println(ret); // 4
}

final var str = Files.readString(target);
System.out.println(str); // abcd

// --- PowerShell ---
//PS D:\java-work> ls -Name
//source.txt
//target.txt

final var source = Path.of("D:", "java-work", "source.txt");
System.out.println(source); // D:\java-work\source.txt

Files.write(source, new byte[]{10, 20, 30});
System.out.println(Files.exists(source)); // true

// --- PowerShell ---
//PS D:\java-work> ls -Name
//source.txt

try (final var out = new ByteArrayOutputStream()) {
    final var ret = Files.copy(source, out);
    System.out.println(ret); // 3

    System.out.println(Arrays.toString(out.toByteArray())); // [10, 20, 30]
}

final var source = Path.of("D:", "java-work", "xxx");
System.out.println(source); // D:\java-work\xxx
System.out.println(Files.notExists(source)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

try (final var out = new ByteArrayOutputStream()) {
    Files.copy(source, out);
} catch (NoSuchFileException e) {
    System.out.println("NoSuchFileException!");
}

// Result
// ↓
//NoSuchFileException!

static Path copy (Path source, Path target, CopyOption... options)

将文件复制到目标文件。 (机器翻译)

final var source = Path.of("D:", "java-work", "source.txt");
System.out.println(source); // D:\java-work\source.txt

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

Files.writeString(source, "abcd");
System.out.println(Files.exists(source)); // true
System.out.println(Files.exists(target)); // false

// --- PowerShell ---
//PS D:\java-work> ls -Name
//source.txt

final var ret = Files.copy(source, target);
System.out.println(ret); // D:\java-work\target.txt

final var str = Files.readString(target);
System.out.println(str); // abcd

// --- PowerShell ---
//PS D:\java-work> ls -Name
//source.txt
//target.txt

final var source = Path.of("D:", "java-work", "source.txt");
System.out.println(source); // D:\java-work\source.txt

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

Files.writeString(source, "abcd");
Files.writeString(target, "XYZ");

System.out.println(Files.readString(source)); // abcd
System.out.println(Files.readString(target)); // XYZ

// --- PowerShell ---
//PS D:\java-work> ls -Name
//source.txt
//target.txt

try {
    Files.copy(source, target);
} catch (FileAlreadyExistsException e) {
    System.out.println("FileAlreadyExistsException!");
}

// Result
// ↓
//FileAlreadyExistsException!

final var ret = Files.copy(source, target, StandardCopyOption.REPLACE_EXISTING);
System.out.println(ret); // D:\java-work\target.txt

System.out.println(Files.readString(source)); // abcd
System.out.println(Files.readString(target)); // abcd

// --- PowerShell ---
//PS D:\java-work> ls -Name
//source.txt
//target.txt

final var source = Path.of("D:", "java-work", "xxx");
System.out.println(source); // D:\java-work\xxx

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

System.out.println(Files.notExists(source)); // true
System.out.println(Files.notExists(target)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

try {
    Files.copy(source, target);
} catch (NoSuchFileException e) {
    System.out.println("NoSuchFileException!");
}

// Result
// ↓
//NoSuchFileException!

static Path createDirectories (Path dir, FileAttribute<?>... attrs)

通过首先创建所有不存在的父目录来创建目录。 (机器翻译)

Please see also createFile(Path path, FileAttribute<?>... attrs) for FileAttribute.

// --- PowerShell ---
//PS D:\java-work> tree /F
//
//D:.

final var dir = Path.of("D:", "java-work", "dir1");
System.out.println(dir); // D:\java-work\dir1
System.out.println(Files.notExists(dir)); // true

final var ret = Files.createDirectories(dir);
System.out.println(ret); // D:\java-work\dir1

System.out.println(Files.isDirectory(dir)); // true

// --- PowerShell ---
//PS D:\java-work> tree /F
//
//D:.
//└─dir1

// --- PowerShell ---
//PS D:\java-work> tree /F
//
//D:.

final var dir = Path.of("D:", "java-work", "dir1", "dir2", "dir3");
System.out.println(dir); // D:\java-work\dir1\dir2\dir3
System.out.println(Files.notExists(dir.getParent().getParent())); // true

final var ret = Files.createDirectories(dir);
System.out.println(ret); // D:\java-work\dir1\dir2\dir3

System.out.println(Files.isDirectory(dir)); // true

// --- PowerShell ---
//PS D:\java-work> tree /F
//
//D:.
//└─dir1
//    └─dir2
//        └─dir3

// --- PowerShell ---
//PS D:\java-work> tree /F
//
//D:.

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir

System.out.println(Files.notExists(dir)); // true
System.out.println(Files.createDirectories(dir)); // D:\java-work\dir

System.out.println(Files.isDirectory(dir)); // true
System.out.println(Files.createDirectories(dir)); // D:\java-work\dir

// --- PowerShell ---
//PS D:\java-work> tree /F
//
//D:.
//└─dir

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.createFile(path);
System.out.println(Files.isDirectory(path)); // false
System.out.println(Files.isRegularFile(path)); // true

// --- PowerShell ---
//PS D:\java-work> tree /F
//
//D:.
//    aaa.txt

try {
    Files.createDirectories(path);
} catch (FileAlreadyExistsException e) {
    System.out.println("FileAlreadyExistsException!");
}

// Result
// ↓
//FileAlreadyExistsException!

static Path createDirectory (Path dir, FileAttribute<?>... attrs)

创建新目录。 (机器翻译)

Please see also createFile(Path path, FileAttribute<?>... attrs) for FileAttribute.

// --- PowerShell ---
//PS D:\java-work> tree /F
//
//D:.

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir
System.out.println(Files.notExists(dir)); // true

final var ret = Files.createDirectory(dir);
System.out.println(ret); // // D:\java-work\dir
System.out.println(Files.isDirectory(dir)); // true

// --- PowerShell ---
//PS D:\java-work> tree /F
//
//D:.
//└─dir

try {
    Files.createDirectory(dir);
} catch (FileAlreadyExistsException e) {
    System.out.println("FileAlreadyExistsException!");
}

// Result
// ↓
//FileAlreadyExistsException!

// --- PowerShell ---
//PS D:\java-work> tree /F
//
//D:.

final var dir = Path.of("D:", "java-work", "dir1", "dir2", "dir3");
System.out.println(dir); // D:\java-work\dir1\dir2\dir3
System.out.println(Files.notExists(dir.getParent())); // true

try {
    Files.createDirectory(dir);
} catch (NoSuchFileException e) {
    System.out.println("NoSuchFileException!");
}

// Result
// ↓
//NoSuchFileException!

static Path createFile (Path path, FileAttribute<?>... attrs)

创建一个新的空文件，如果该文件已经存在则失败。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt
System.out.println(Files.notExists(path)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

final var ret = Files.createFile(path);
System.out.println(ret); // D:\java-work\aaa.txt
System.out.println(Files.size(path)); // 0

// --- PowerShell ---
//PS D:\java-work> ls -Name
//aaa.txt

try {
    Files.createFile(path);
} catch (FileAlreadyExistsException e) {
    System.out.println("FileAlreadyExistsException!");
}

// Result
// ↓
//FileAlreadyExistsException!

final var path = Path.of("D:", "java-work", "dir", "aaa.txt");
System.out.println(path); // D:\java-work\dir\aaa.txt
System.out.println(Files.notExists(path)); // true

final var parent = path.getParent();
System.out.println(parent); // D:\java-work\dir
System.out.println(Files.notExists(parent)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

try {
    Files.createFile(path);
} catch (NoSuchFileException e) {
    System.out.println("NoSuchFileException!");
}

// Result
// ↓
//NoSuchFileException!

The following code runs on Linux.

System.out.println(System.getProperty("os.name")); // Linux

final var ret1 = Files.createFile(Path.of("sample1.txt"));
System.out.println(ret1); // sample1.txt

// --- Linux Terminal ---
//$ ls -l sample1.txt
//-rw-rw-r-- 1 xxxx xxxx 0 ... sample1.txt

final var permissions = PosixFilePermissions.fromString("rw-r-----");
System.out.println(permissions); // [OWNER_READ, OWNER_WRITE, GROUP_READ]

final var ret2 = Files.createFile(
        Path.of("sample2.txt"),
        PosixFilePermissions.asFileAttribute(permissions));
System.out.println(ret2); // sample2.txt

// --- Linux Terminal ---
//$ ls -l sample2.txt
//-rw-r----- 1 xxxx xxxx 0 ... sample2.txt

static Path createLink (Path link, Path existing)

为现有文件创建新的链接（目录条目）（可选操作）。 (机器翻译)

final var existing = Path.of("D:", "java-work", "existing.txt");
System.out.println(existing); // D:\java-work\existing.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.writeString(existing, "abcd");
System.out.println(Files.exists(existing)); // true
System.out.println(Files.exists(link)); // false

// --- PowerShell ---
//PS D:\java-work> ls -Name
//existing.txt

final var ret = Files.createLink(link, existing);
System.out.println(ret); // D:\java-work\link.txt

System.out.println(Files.readString(existing)); // abcd
System.out.println(Files.readString(link)); // abcd

// --- PowerShell ---
//PS D:\java-work> ls -Name
//existing.txt
//link.txt
//
//PS D:\java-work> ls .\link.txt | Format-List
//...
//Mode           : la---
//LinkType       : HardLink
//Target         :
//VersionInfo    : File:             D:\java-work\link.txt
//...

Files.writeString(existing, "XYZ");

System.out.println(Files.readString(existing)); // XYZ
System.out.println(Files.readString(link)); // XYZ

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

final var existing = Path.of("D:", "java-work", "existing.txt");
System.out.println(existing); // D:\java-work\existing.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

System.out.println(Files.notExists(existing)); // true
System.out.println(Files.notExists(link)); // true

try {
    Files.createLink(link, existing); // NoSuchFileException
} catch (NoSuchFileException e) {
    System.out.println("NoSuchFileException!");
}

// Result
// ↓
//NoSuchFileException!

final var existing = Path.of("D:", "java-work", "existing.txt");
System.out.println(existing); // D:\java-work\existing.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.createFile(existing);
Files.createFile(link);
System.out.println(Files.exists(existing)); // true
System.out.println(Files.exists(link)); // true

// --- PowerShell ---
//PS D:\java-work> ls -Name
//existing.txt
//link.txt

try {
    Files.createLink(link, existing);
} catch (FileAlreadyExistsException e) {
    System.out.println("FileAlreadyExistsException!");
}

// Result
// ↓
//FileAlreadyExistsException!

static Path createSymbolicLink (Path link, Path target, FileAttribute<?>... attrs)

创建到目标的符号链接（可选操作）。 (机器翻译)

Creating a symbolic link may require administrator privileges.

Please see also createFile(Path path, FileAttribute<?>... attrs) for FileAttribute.

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.writeString(target, "abcd");
System.out.println(Files.exists(target)); // true
System.out.println(Files.exists(link)); // false

// --- PowerShell ---
//PS D:\java-work> ls -Name
//target.txt

final var ret = Files.createSymbolicLink(link, target);
System.out.println(ret); // D:\java-work\link.txt

System.out.println(Files.readString(target)); // abcd
System.out.println(Files.readString(link)); // abcd

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//la---  ...        0 link.txt -> D:\java-work\target.txt
//-a---  ...        4 target.txt
//
//PS D:\java-work> ls .\link.txt | Format-List
//...
//Mode           : la---
//LinkType       : SymbolicLink
//Target         : D:\java-work\target.txt
//VersionInfo    : File:             D:\java-work\link.txt
//...

Files.writeString(target, "XYZ");

System.out.println(Files.readString(target)); // XYZ
System.out.println(Files.readString(link)); // XYZ

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

System.out.println(Files.notExists(target)); // true
System.out.println(Files.notExists(link)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

// You can also create empty links.
final var ret = Files.createSymbolicLink(link, target);
System.out.println(ret); // D:\java-work\link.txt

System.out.println(Files.notExists(target)); // true
System.out.println(Files.notExists(link)); // true
System.out.println(Files.isSymbolicLink(link)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//la---  ...        0 link.txt -> D:\java-work\target.txt

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.createFile(target);
Files.createFile(link);
System.out.println(Files.exists(target)); // true
System.out.println(Files.exists(link)); // true

// --- PowerShell ---
//PS D:\java-work> ls -Name
//link.txt
//target.txt

try {
    Files.createSymbolicLink(link, target);
} catch (FileAlreadyExistsException e) {
    System.out.println("FileAlreadyExistsException!");
}

// Result
// ↓
//FileAlreadyExistsException!

static Path createTempDirectory (String prefix, FileAttribute<?>... attrs)

在默认临时文件目录中创建一个新目录，并使用给定的前缀生成其名称。 (机器翻译)

Please see also createFile(Path path, FileAttribute<?>... attrs) for FileAttribute.

final var ret1 = Files.createTempDirectory("prefix");
System.out.println(ret1); // C:\Users\xxx\AppData\Local\Temp\prefix6089636834939322082

final var ret2 = Files.createTempDirectory("abcd-");
System.out.println(ret2); // C:\Users\xxx\AppData\Local\Temp\abcd-6998169258402534775

final var ret3 = Files.createTempDirectory(null);
System.out.println(ret3); // C:\Users\xxx\AppData\Local\Temp\7916867536894745055

static Path createTempDirectory (Path dir, String prefix, FileAttribute<?>... attrs)

在指定目录中创建一个新目录，并使用给定的前缀生成其名称。 (机器翻译)

Please see also createFile(Path path, FileAttribute<?>... attrs) for FileAttribute.

final var dir = Path.of("D:", "java-work");
System.out.println(dir); // D:\java-work

final var ret1 = Files.createTempDirectory(dir, "prefix");
System.out.println(ret1); // D:\java-work\prefix18208067467997933175

final var ret2 = Files.createTempDirectory(dir, "abcd-");
System.out.println(ret2); // D:\java-work\abcd-521471602431667304

final var ret3 = Files.createTempDirectory(dir, null);
System.out.println(ret3); // D:\java-work\2640746303774778924

static Path createTempFile (String prefix, String suffix, FileAttribute<?>... attrs)

在默认临时文件目录中创建一个空文件，使用给定的前缀和后缀生成其名称。 (机器翻译)

Please see also createFile(Path path, FileAttribute<?>... attrs) for FileAttribute.

final var ret1 = Files.createTempFile("prefix-", "-suffix");
System.out.println(ret1); // C:\Users\xxx\AppData\Local\Temp\prefix-9091722447586283597-suffix

final var ret2 = Files.createTempFile("abcd-", ".txt");
System.out.println(ret2); // C:\Users\xxx\AppData\Local\Temp\abcd-13867786695402679957.txt

final var ret3 = Files.createTempFile("prefix-", null);
System.out.println(ret3); // C:\Users\xxx\AppData\Local\Temp\prefix-17221573028074243598.tmp

final var ret4 = Files.createTempFile(null, "-suffix");
System.out.println(ret4); // C:\Users\xxx\AppData\Local\Temp\11809310207624726987-suffix

final var ret5 = Files.createTempFile(null, null);
System.out.println(ret5); // C:\Users\xxx\AppData\Local\Temp\13779039011143750638.tmp

static Path createTempFile (Path dir, String prefix, String suffix, FileAttribute<?>... attrs)

在指定目录中创建一个新的空文件，使用给定的前缀和后缀字符串生成其名称。 (机器翻译)

Please see also createFile(Path path, FileAttribute<?>... attrs) for FileAttribute.

final var dir = Path.of("D:", "java-work");
System.out.println(dir); // D:\java-work

final var ret1 = Files.createTempFile(dir, "prefix-", "-suffix");
System.out.println(ret1); // D:\java-work\prefix-10113412430119575991-suffix

final var ret2 = Files.createTempFile(dir, "abcd-", ".txt");
System.out.println(ret2); // D:\java-work\abcd-169546499978120138.txt

final var ret3 = Files.createTempFile(dir, "prefix-", null);
System.out.println(ret3); // D:\java-work\prefix-9437871265568200345.tmp

final var ret4 = Files.createTempFile(dir, null, "-suffix");
System.out.println(ret4); // D:\java-work\9337658086830323119-suffix

final var ret5 = Files.createTempFile(dir, null, null);
System.out.println(ret5); // D:\java-work\13108613127478405635.tmp

static void delete (Path path)

删除文件。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir

Files.createFile(path);
Files.createDirectory(dir);

System.out.println(Files.isRegularFile(path)); // true
System.out.println(Files.isDirectory(dir)); // true

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//d---- dir
//-a--- aaa.txt

Files.delete(path);
System.out.println(Files.notExists(path)); // true

//PS D:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//d---- dir

Files.delete(dir);
System.out.println(Files.notExists(dir)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(Files.notExists(path)); // true

try {
    Files.delete(path);
} catch (NoSuchFileException e) {
    System.out.println("NoSuchFileException!");
}

// Result
// ↓
//NoSuchFileException!

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//└─dir
//        aaa.txt
//        bbb.txt

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir
System.out.println(Files.isDirectory(dir)); // true

try {
    Files.delete(dir);
} catch (DirectoryNotEmptyException e) {
    System.out.println("DirectoryNotEmptyException!");
}

// Result
// ↓
//DirectoryNotEmptyException!

static boolean deleteIfExists (Path path)

如果文件存在则删除它。 (机器翻译)

Please see also : delete(Path path)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.createFile(path);
System.out.println(Files.exists(path)); // true

// --- PowerShell ---
//PS D:\java-work> ls -Name
//aaa.txt

System.out.println(Files.deleteIfExists(path)); // true
System.out.println(Files.notExists(path)); // true

// --- PowerShell ---
//PS D:\java-work> ls -Name
//<No files / directories>

System.out.println(Files.deleteIfExists(path)); // false

static boolean exists (Path path, LinkOption... options)

测试文件是否存在。 (机器翻译)

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir

final var file = Path.of("D:", "java-work", "aaa.txt");
System.out.println(file); // D:\java-work\aaa.txt

final var nonExistentPath = Path.of("D:", "java-work", "xxx");
System.out.println(nonExistentPath); // D:\java-work\xxx

Files.createDirectory(dir);
Files.createFile(file);

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//d---- dir
//-a--- aaa.txt

System.out.println(Files.isDirectory(dir)); // true
System.out.println(Files.exists(dir)); // true

System.out.println(Files.isRegularFile(file)); // true
System.out.println(Files.exists(file)); // true

System.out.println(Files.exists(nonExistentPath)); // false

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

// Intentionally creates an empty link.
Files.createSymbolicLink(link, target);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//la---  ...        0 link.txt -> D:\java-work\target.txt

System.out.println(Files.exists(target)); // false

System.out.println(Files.isSymbolicLink(link)); // true
System.out.println(Files.exists(link)); // false
System.out.println(Files.exists(link, LinkOption.NOFOLLOW_LINKS)); // true

static Stream<Path> find (Path start, int maxDepth, BiPredicate<Path,BasicFileAttributes> matcher, FileVisitOption... options)

通过在以给定起始文件为根的文件树中搜索文件，返回一个用路径延迟填充的流。 (机器翻译)

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//│  aaa.txt
//│  bbb.txt
//│
//├─dir1
//│  │  ccc.txt
//│  │  ddd.txt
//│  │
//│  └─dir1-2
//│          eee.txt
//│          fff.txt
//│
//└─dir2
//        ggg.txt
//        hhh.txt

final var start = Path.of("D:", "java-work");
System.out.println(start); // D:\java-work

System.out.println("maxDepth : 3");
try (final var stream = Files.find(start, 3, (_, _) -> true)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//maxDepth : 3
//D:\java-work
//D:\java-work\aaa.txt
//D:\java-work\bbb.txt
//D:\java-work\dir1
//D:\java-work\dir1\ccc.txt
//D:\java-work\dir1\ddd.txt
//D:\java-work\dir1\dir1-2
//D:\java-work\dir1\dir1-2\eee.txt
//D:\java-work\dir1\dir1-2\fff.txt
//D:\java-work\dir2
//D:\java-work\dir2\ggg.txt
//D:\java-work\dir2\hhh.txt

System.out.println("maxDepth : 2");
try (final var stream = Files.find(start, 2, (_, _) -> true)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//maxDepth : 2
//D:\java-work
//D:\java-work\aaa.txt
//D:\java-work\bbb.txt
//D:\java-work\dir1
//D:\java-work\dir1\ccc.txt
//D:\java-work\dir1\ddd.txt
//D:\java-work\dir1\dir1-2
//D:\java-work\dir2
//D:\java-work\dir2\ggg.txt
//D:\java-work\dir2\hhh.txt

System.out.println("maxDepth : 1");
try (final var stream = Files.find(start, 1, (_, _) -> true)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//maxDepth : 1
//D:\java-work
//D:\java-work\aaa.txt
//D:\java-work\bbb.txt
//D:\java-work\dir1
//D:\java-work\dir2

System.out.println("maxDepth : 0");
try (final var stream = Files.find(start, 0, (_, _) -> true)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//maxDepth : 0
//D:\java-work

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//│  aaa.txt
//│  bbb.txt
//│
//├─dir1
//│  │  ccc.txt
//│  │  ddd.txt
//│  │
//│  └─dir1-2
//│          eee.txt
//│          fff.txt
//│
//└─dir2
//        ggg.txt
//        hhh.txt

final var start = Path.of("D:", "java-work");
System.out.println(start); // D:\java-work

System.out.println("matcher : isDirectory");
try (final var stream = Files.find(start, Integer.MAX_VALUE,
        (_, basicFileAttributes) -> basicFileAttributes.isDirectory())) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//matcher : isDirectory
//D:\java-work
//D:\java-work\dir1
//D:\java-work\dir1\dir1-2
//D:\java-work\dir2

System.out.println("matcher : isRegularFile");
try (final var stream = Files.find(start, Integer.MAX_VALUE,
        (_, basicFileAttributes) -> basicFileAttributes.isRegularFile())) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//matcher : isRegularFile
//D:\java-work\aaa.txt
//D:\java-work\bbb.txt
//D:\java-work\dir1\ccc.txt
//D:\java-work\dir1\ddd.txt
//D:\java-work\dir1\dir1-2\eee.txt
//D:\java-work\dir1\dir1-2\fff.txt
//D:\java-work\dir2\ggg.txt
//D:\java-work\dir2\hhh.txt

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//├─dir
//│      aaa.txt
//│      bbb.txt
//│
//└─link-dir
//        aaa.txt
//        bbb.txt
//
//PS D:\java-work> ls
//
//    Directory: D:\java-work
//
//Mode   ...   Length Name
//----   ...   ------ ----
//d----  ...          dir
//l----  ...          link-dir -> D:\java-work\dir

final var start = Path.of("D:", "java-work");
System.out.println(start); // D:\java-work

try (final var stream = Files.find(start, Integer.MAX_VALUE,
        (_, _) -> true)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//D:\java-work
//D:\java-work\dir
//D:\java-work\dir\aaa.txt
//D:\java-work\dir\bbb.txt
//D:\java-work\link-dir

System.out.println("FileVisitOption : FOLLOW_LINKS");
try (final var stream = Files.find(start, Integer.MAX_VALUE,
        (_, _) -> true, FileVisitOption.FOLLOW_LINKS)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//FileVisitOption : FOLLOW_LINKS
//D:\java-work
//D:\java-work\dir
//D:\java-work\dir\aaa.txt
//D:\java-work\dir\bbb.txt
//D:\java-work\link-dir
//D:\java-work\link-dir\aaa.txt
//D:\java-work\link-dir\bbb.txt

final var start = Path.of("D:", "java-work", "xxx");
System.out.println(start); // D:\java-work\xxx
System.out.println(Files.notExists(start)); // true

try (var _ = Files.find(start, Integer.MAX_VALUE, (_, _) -> true)) {
    System.out.println("No errors");
} catch (NoSuchFileException e) {
    System.out.println("NoSuchFileException!");
}

// Result
// ↓
//NoSuchFileException!

static Object getAttribute (Path path, String attribute, LinkOption... options)

读取文件属性的值。 (机器翻译)

final var file = Path.of("D:", "java-work", "aaa.txt");
System.out.println(file); // D:\java-work\aaa.txt

final var hidden = Path.of("D:", "java-work", "hidden.txt");
System.out.println(hidden); // D:\java-work\hidden.txt

Files.writeString(file, "abcd");

Files.writeString(hidden, "1234567890");
Files.setAttribute(hidden, "dos:hidden", true);

// --- PowerShell ---
//PS D:\java-work> ls -Force | Format-Table -Property Mode, Length, Name
//
//Mode  Length Name
//----  ------ ----
//-a---      4 aaa.txt
//-a-h-     10 hidden.txt

System.out.println(Files.getAttribute(file, "size")); // 4
System.out.println(Files.getAttribute(hidden, "size")); // 10

System.out.println(Files.getAttribute(file, "dos:hidden")); // false
System.out.println(Files.getAttribute(hidden, "dos:hidden")); // true

final var target = Path.of("D:", "java-work", "aaa.txt");
System.out.println(target); // D:\java-work\aaa.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.writeString(target, "abcd");
Files.createSymbolicLink(link, target);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//-a---  ...        4 aaa.txt
//la---  ...        0 link.txt -> D:\java-work\aaa.txt

System.out.println(Files.getAttribute(link, "size")); // 4
System.out.println(Files.getAttribute(link, "size", LinkOption.NOFOLLOW_LINKS)); // 0

static <V extends FileAttributeView> V getFileAttributeView (Path path, Class<V> type, LinkOption... options)

返回给定类型的文件属性视图。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.writeString(path, "abcd");

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property Mode, Length, Name
//
//Mode  Length Name
//----  ------ ----
//-a---      4 aaa.txt

final var basicView = Files.getFileAttributeView(path, BasicFileAttributeView.class);
if (basicView != null) {
    final var attrs = basicView.readAttributes();
    System.out.println(attrs.size()); // 4
    System.out.println(attrs.isRegularFile()); // true
    System.out.println(attrs.isDirectory()); // false
}

final var hidden = Path.of("D:", "java-work", "hidden.txt");
System.out.println(hidden); // D:\java-work\hidden.txt

Files.writeString(hidden, "abcd");
Files.setAttribute(hidden, "dos:hidden", true);

// --- PowerShell ---
//PS D:\java-work> ls -Force | Format-Table -Property Mode, Length, Name
//
//Mode  Length Name
//----  ------ ----
//-a-h-      4 hidden.txt

final var dosView = Files.getFileAttributeView(hidden, DosFileAttributeView.class);
if (dosView != null) {
    final var attrs = dosView.readAttributes();
    System.out.println(attrs.size()); // 4
    System.out.println(attrs.isHidden()); // true
    System.out.println(attrs.isReadOnly()); // false

    dosView.setReadOnly(true);

    // --- PowerShell ---
    //PS D:\java-work> ls -Force | Format-Table -Property Mode, Length, Name
    //
    //Mode  Length Name
    //----  ------ ----
    //-arh-      4 hidden.txt
}

final var target = Path.of("D:", "java-work", "aaa.txt");
System.out.println(target); // D:\java-work\aaa.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.writeString(target, "abcd");
Files.createSymbolicLink(link, target);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//-a---  ...        4 aaa.txt
//la---  ...        0 link.txt -> D:\java-work\aaa.txt

final var basicView = Files.getFileAttributeView(
        link, BasicFileAttributeView.class);
if (basicView != null) {
    final var attrs = basicView.readAttributes();
    System.out.println(attrs.size()); // 4
    System.out.println(attrs.isRegularFile()); // true
    System.out.println(attrs.isSymbolicLink()); // false
}

final var basicView2 = Files.getFileAttributeView(
        link, BasicFileAttributeView.class, LinkOption.NOFOLLOW_LINKS);
if (basicView2 != null) {
    final var attrs = basicView2.readAttributes();
    System.out.println(attrs.size()); // 0
    System.out.println(attrs.isRegularFile()); // false
    System.out.println(attrs.isSymbolicLink()); // true
}

static FileStore getFileStore (Path path)

返回代表文件所在文件存储的 FileStore。 (机器翻译)

final var path = Path.of("D:", "java-work");
System.out.println(path); // D:\java-work

final var store = Files.getFileStore(path);

System.out.println(store.type()); // NTFS
System.out.println(store.getBlockSize()); // 512

static FileTime getLastModifiedTime (Path path, LinkOption... options)

返回文件的最后修改时间。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.createFile(path);

final var zoneId = ZoneId.systemDefault();
System.out.println(zoneId); // Asia/Tokyo

final var ret = Files.setLastModifiedTime(path, FileTime.from(
        ZonedDateTime.of(2100, 1, 1, 0, 0, 0, 0, zoneId).toInstant()));
System.out.println(ret); // D:\java-work\aaa.txt

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property LastWriteTime, Name
//
//LastWriteTime      Name
//-------------      ----
//2100/01/01 0:00:00 aaa.txt

// FileTime is UTC.
final var fileTime = Files.getLastModifiedTime(path);
System.out.println(fileTime); // 2099-12-31T15:00:00Z

final var zonedDateTime = ZonedDateTime.ofInstant(fileTime.toInstant(), zoneId);
System.out.println(zonedDateTime); // 2100-01-01T00:00+09:00[Asia/Tokyo]

final var target = Path.of("D:", "java-work", "aaa.txt");
System.out.println(target); // D:\java-work\aaa.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

final var zoneId = ZoneId.systemDefault();
System.out.println(zoneId); // Asia/Tokyo

final var zonedDateTime = ZonedDateTime.of(2100, 1, 1, 0, 0, 0, 0, zoneId);
System.out.println(zonedDateTime); // 2100-01-01T00:00+09:00[Asia/Tokyo]

Files.createFile(target);
Files.setLastModifiedTime(target, FileTime.from(zonedDateTime.toInstant()));

Files.createSymbolicLink(link, target);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode                 LastWriteTime         Length Name
//----                 -------------         ------ ----
//-a---          2100/01/01     0:00              0 aaa.txt
//la---          2024/10/19    16:31              0 link.txt -> D:\java-work\aaa.txt

final var ret1 = Files.getLastModifiedTime(link);
System.out.println(ret1); // 2099-12-31T15:00:00Z

final var ret2 = Files.getLastModifiedTime(link, LinkOption.NOFOLLOW_LINKS);
System.out.println(ret2); // 2024-10-19T07:31:55.9393338Z

static UserPrincipal getOwner (Path path, LinkOption... options)

返回文件的所有者。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.createFile(path);

final var service = path.getFileSystem().getUserPrincipalLookupService();
final var newOwner = service.lookupPrincipalByName("test-user");

final var ret1 = Files.setOwner(path, newOwner);
System.out.println(ret1); // D:\java-work\aaa.txt

// --- PowerShell ---
//PS D:\java-work> Get-Acl .\aaa.txt
//...
//Path    Owner           Access
//----    -----           ------
//aaa.txt MY-PC\test-user BUILTIN\Administrators Allow  FullControl…

final var ret2 = Files.getOwner(path);
System.out.println(ret2); // MY-PC\test-user (User)

final var target = Path.of("D:", "java-work", "aaa.txt");
System.out.println(target); // D:\java-work\aaa.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.createSymbolicLink(link, target);

// --- PowerShell ---
//PS D:\java-work> ls | Get-Acl
//..
//Path     Owner                    Access
//----     -----                    ------
//aaa.txt  MY-PC\test-user          BUILTIN\Administrators Allow  FullControl…
//link.txt BUILTIN\Administrators   BUILTIN\Administrators Allow  FullControl…

final var ret1 = Files.getOwner(link);
System.out.println(ret1); // MY-PC\test-user (User)

final var ret2 = Files.getOwner(link, LinkOption.NOFOLLOW_LINKS);
System.out.println(ret2); // BUILTIN\Administrators (Alias)

static Set<PosixFilePermission> getPosixFilePermissions (Path path, LinkOption... options)

返回文件的 POSIX 文件权限。 (机器翻译)

The following code runs on Linux.

System.out.println(System.getProperty("os.name")); // Linux

// --- Linux Terminal ---
//$ ls -l sample.txt
//-rw-rw-r-- 1 xxxx xxxx 0 ... sample.txt

final var path = Path.of("sample.txt");

final var permissions = Files.getPosixFilePermissions(path);
System.out.println(PosixFilePermissions.toString(permissions)); // rw-rw-r--

System.out.println(System.getProperty("os.name")); // Linux

// --- Linux Terminal ---
//$ ls -l
//lrwxrwxrwx 1 xxxx xxxx 10 ... link.txt -> sample.txt
//-rw-rw-r-- 1 xxxx xxxx  0 ... sample.txt

final var path = Path.of("link.txt");

final var permissions1 = Files.getPosixFilePermissions(path);
System.out.println(PosixFilePermissions.toString(permissions1)); // rw-rw-r--

final var permissions2 = Files.getPosixFilePermissions(path, LinkOption.NOFOLLOW_LINKS);
System.out.println(PosixFilePermissions.toString(permissions2)); // rwxrwxrwx

static boolean isDirectory (Path path, LinkOption... options)

测试文件是否是目录。 (机器翻译)

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir

final var file = Path.of("D:", "java-work", "aaa.txt");
System.out.println(file); // D:\java-work\aaa.txt

final var link = Path.of("D:", "java-work", "link-dir");
System.out.println(link); // D:\java-work\link-dir

final var nonExistentPath = Path.of("D:", "java-work", "xxx");
System.out.println(nonExistentPath); // D:\java-work\xxx

Files.createDirectory(dir);
Files.createFile(file);
Files.createSymbolicLink(link, dir);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//d----  ...          dir
//l----  ...          link-dir -> D:\java-work\dir
//-a---  ...        0 aaa.txt

System.out.println(Files.isDirectory(dir)); // true
System.out.println(Files.isDirectory(file)); // false

System.out.println(Files.isDirectory(link)); // true
System.out.println(Files.isDirectory(link, LinkOption.NOFOLLOW_LINKS)); // false

System.out.println(Files.isDirectory(nonExistentPath)); // false

static boolean isExecutable (Path path)

测试文件是否可执行。 (机器翻译)

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir

final var file = Path.of("D:", "java-work", "aaa.txt");
System.out.println(file); // D:\java-work\aaa.txt

final var exe = Path.of("D:", "java-work", "java.exe");
System.out.println(exe); // D:\java-work\java.exe

final var nonExistentPath = Path.of("D:", "java-work", "xxx");
System.out.println(nonExistentPath); // D:\java-work\xxx

Files.createDirectory(dir);
Files.createFile(file);
Files.copy(Path.of(System.getProperty("java.home"), "bin", "java.exe"), exe);

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//d---- dir
//-a--- aaa.txt
//-a--- java.exe

// On Windows.
System.out.println(Files.isExecutable(dir)); // true
System.out.println(Files.isExecutable(file)); // true
System.out.println(Files.isExecutable(exe)); // true
System.out.println(Files.isExecutable(nonExistentPath)); // false

The following code runs on Linux.

System.out.println(System.getProperty("os.name")); // Linux

final var shFile = Path.of("sample.sh");
final var txtFile = Path.of("sample.txt");

// --- Linux Terminal ---
//$ ls -l
//-rwxrwxr-x 1 xxxx xxxx    0 ... sample.sh
//-rw-rw-r-- 1 xxxx xxxx    0 ... sample.txt

System.out.println(Files.isExecutable(shFile)); // true
System.out.println(Files.isExecutable(txtFile)); // false

static boolean isHidden (Path path)

判断文件是否被视为隐藏。 (机器翻译)

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir

final var file = Path.of("D:", "java-work", "aaa.txt");
System.out.println(file); // D:\java-work\aaa.txt

final var hidden = Path.of("D:", "java-work", "hidden.txt");
System.out.println(hidden); // D:\java-work\hidden.txt

Files.createDirectory(dir);
Files.createFile(file);

Files.createFile(hidden);
Files.setAttribute(hidden, "dos:hidden", true);

// --- PowerShell ---
//PS D:\java-work> ls -Force | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//d---- dir
//-a--- aaa.txt
//-a-h- hidden.txt

System.out.println(Files.isHidden(dir)); // false
System.out.println(Files.isHidden(file)); // false
System.out.println(Files.isHidden(hidden)); // true

final var nonExistentPath = Path.of("D:", "java-work", "xxx");
System.out.println(nonExistentPath); // D:\java-work\xxx
System.out.println(Files.notExists(nonExistentPath)); // true

try {
    Files.isHidden(nonExistentPath);
} catch (NoSuchFileException e) {
    System.out.println("NoSuchFileException!");
}

// Result
// ↓
//NoSuchFileException!

static boolean isReadable (Path path)

测试文件是否可读。 (机器翻译)

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir

final var file = Path.of("D:", "java-work", "aaa.txt");
System.out.println(file); // D:\java-work\aaa.txt

final var nonExistentPath = Path.of("D:", "java-work", "xxx");
System.out.println(nonExistentPath); // D:\java-work\xxx

Files.createDirectory(dir);
Files.createFile(file);

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//d---- dir
//-a--- aaa.txt

System.out.println(Files.isReadable(dir)); // true
System.out.println(Files.isReadable(file)); // true
System.out.println(Files.isReadable(nonExistentPath)); // false

// The non-readable.txt has read permission denied.
final var nonReadableFile = Path.of("D:", "java-work", "non-readable.txt");
System.out.println(nonReadableFile); // D:\java-work\non-readable.txt

// --- PowerShell ---
//PS D:\java-work> Get-Acl .\non-readable.txt
//...
//Path             Owner           Access
//----             -----           ------
//non-readable.txt MY-PC\test-user BUILTIN\Administrators Deny  ReadData…

System.out.println(Files.isReadable(nonReadableFile)); // false

static boolean isRegularFile (Path path, LinkOption... options)

测试文件是否是具有不透明内容的常规文件。 (机器翻译)

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir

final var file = Path.of("D:", "java-work", "aaa.txt");
System.out.println(file); // D:\java-work\aaa.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

final var nonExistentPath = Path.of("D:", "java-work", "xxx");
System.out.println(nonExistentPath); // D:\java-work\xxx

Files.createDirectory(dir);
Files.createFile(file);
Files.createSymbolicLink(link, file);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//d----  ...          dir
//-a---  ...        0 aaa.txt
//la---  ...        0 link.txt -> D:\java-work\aaa.txt

System.out.println(Files.isDirectory(dir)); // true
System.out.println(Files.isRegularFile(dir)); // false

System.out.println(Files.exists(file)); // true
System.out.println(Files.isRegularFile(file)); // true

System.out.println(Files.isSymbolicLink(link)); // true
System.out.println(Files.isRegularFile(link)); // true
System.out.println(Files.isRegularFile(link, LinkOption.NOFOLLOW_LINKS)); // false

System.out.println(Files.notExists(nonExistentPath)); // true
System.out.println(Files.isRegularFile(nonExistentPath)); // false

static boolean isSameFile (Path path, Path path2)

测试两个路径是否位于同一个文件。 (机器翻译)

final var file1 = Path.of("D:", "java-work", "aaa1.txt");
System.out.println(file1); // D:\java-work\aaa1.txt

final var file2 = Path.of("D:", "java-work", "aaa2.txt");
System.out.println(file2); // D:\java-work\aaa2.txt

final var file3 = Path.of("D:", "java-work", "bbb.txt");
System.out.println(file3); // D:\java-work\bbb.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.writeString(file1, "abcd");
Files.writeString(file2, "abcd");
Files.writeString(file3, "XYZ");
Files.createSymbolicLink(link, file1);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//-a---  ...        4 aaa1.txt
//-a---  ...        4 aaa2.txt
//-a---  ...        3 bbb.txt
//la---  ...        0 link.txt -> D:\java-work\aaa1.txt

System.out.println(Files.readString(file1)); // abcd
System.out.println(Files.readString(file2)); // abcd
System.out.println(Files.readString(file3)); // XYZ
System.out.println(Files.readString(link)); // abcd

System.out.println(Files.isSameFile(file1, file1)); // true
System.out.println(Files.isSameFile(file1, file2)); // false
System.out.println(Files.isSameFile(file1, file3)); // false
System.out.println(Files.isSameFile(file1, link)); // true

final var file = Path.of("D:", "java-work", "aaa.txt");
System.out.println(file); // D:\java-work\aaa.txt

final var nonExistentPath = Path.of("D:", "java-work", "xxx");
System.out.println(nonExistentPath); // D:\java-work\xxx

Files.createFile(file);

// --- PowerShell ---
//PS D:\java-work> ls -Name
//aaa.txt

try {
    Files.isSameFile(file, nonExistentPath);
} catch (NoSuchFileException e) {
    System.out.println("NoSuchFileException!");
}

// Result
// ↓
//NoSuchFileException!

static boolean isSymbolicLink (Path path)

测试文件是否是符号链接。 (机器翻译)

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir

final var file = Path.of("D:", "java-work", "aaa.txt");
System.out.println(file); // D:\java-work\aaa.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

final var nonExistentPath = Path.of("D:", "java-work", "xxx");
System.out.println(nonExistentPath); // D:\java-work\xxx

Files.createDirectory(dir);
Files.createFile(file);
Files.createSymbolicLink(link, file);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//d----  ...          dir
//-a---  ...        0 aaa.txt
//la---  ...        0 link.txt -> D:\java-work\aaa.txt

System.out.println(Files.isDirectory(dir)); // true
System.out.println(Files.isSymbolicLink(dir)); // false

System.out.println(Files.isRegularFile(file)); // true
System.out.println(Files.isSymbolicLink(file)); // false

System.out.println(Files.exists(link)); // true
System.out.println(Files.isSymbolicLink(link)); // true

System.out.println(Files.notExists(nonExistentPath)); // true
System.out.println(Files.isSymbolicLink(nonExistentPath)); // false

static boolean isWritable (Path path)

测试文件是否可写。 (机器翻译)

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir

final var file = Path.of("D:", "java-work", "aaa.txt");
System.out.println(file); // D:\java-work\aaa.txt

final var readOnlyFile = Path.of("D:", "java-work", "read-only.txt");
System.out.println(readOnlyFile); // D:\java-work\read-only.txt

final var nonExistentPath = Path.of("D:", "java-work", "xxx");
System.out.println(nonExistentPath); // D:\java-work\xxx

Files.createDirectory(dir);
Files.createFile(file);

Files.createFile(readOnlyFile);
Files.setAttribute(readOnlyFile, "dos:readonly", true);

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//d---- dir
//-a--- aaa.txt
//-ar-- read-only.txt

System.out.println(Files.isDirectory(dir)); // true
System.out.println(Files.isWritable(dir)); // true

System.out.println(Files.isRegularFile(file)); // true
System.out.println(Files.isWritable(file)); // true

System.out.println(Files.isRegularFile(readOnlyFile)); // true
System.out.println(Files.isWritable(readOnlyFile)); // false

System.out.println(Files.notExists(nonExistentPath)); // true
System.out.println(Files.isWritable(nonExistentPath)); // false

static Stream<String> lines (Path path)

从文件读取所有行作为流。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.writeString(path, """
        abcd
        XYZ
        12345
        """);

try (final var lines = Files.lines(path)) {
    System.out.println(lines.toList()); // [abcd, XYZ, 12345]
}

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.createFile(path);
System.out.println(Files.size(path)); // 0

try (final var stream = Files.lines(path)) {
    System.out.println(stream.toList()); // []
}

static Stream<String> lines (Path path, Charset cs)

从文件读取所有行作为流。 (机器翻译)

Please see also : lines(Path path)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path);

final var csq = """
        abcd
        12345
        〇△□×
        """;

Files.writeString(path, csq, StandardCharsets.UTF_8);

try (final var stream = Files.lines(path, StandardCharsets.UTF_8)) {
    System.out.println(stream.toList()); // [abcd, 12345, 〇△□×]
}

try (final var stream = Files.lines(path, Charset.forName("Shift_JIS"))) {
    var _ = stream.toList();
} catch (UncheckedIOException e) {
    System.out.println("UncheckedIOException! : " + e.getMessage());
}

// Result
// ↓
//UncheckedIOException! : java.nio.charset.MalformedInputException: Input length = 1

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path);

final var csq = """
        abcd
        12345
        〇△□×
        """;

Files.writeString(path, csq, Charset.forName("Shift_JIS"));

try (final var stream = Files.lines(path, Charset.forName("Shift_JIS"))) {
    System.out.println(stream.toList()); // [abcd, 12345, 〇△□×]
}

try (final var stream = Files.lines(path, StandardCharsets.UTF_8)) {
    var _ = stream.toList();
} catch (UncheckedIOException e) {
    System.out.println("UncheckedIOException! : " + e.getMessage());
}

// Result
// ↓
//UncheckedIOException! : java.nio.charset.MalformedInputException: Input length = 1

static Stream<Path> list (Path dir)

返回一个延迟填充的 Stream，其元素是目录中的条目。 (机器翻译)

final var dir1 = Path.of("D:", "java-work");
System.out.println(dir1); // D:\java-work

Files.createFile(dir1.resolve(Path.of("aaa.txt")));
Files.createFile(dir1.resolve(Path.of("bbb.txt")));

final var dir2 = dir1.resolve("dir");
System.out.println(dir2); // D:\java-work\dir

Files.createDirectory(dir2);
Files.createFile(dir2.resolve(Path.of("ccc.txt")));
Files.createFile(dir2.resolve(Path.of("ddd.txt")));

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//│  aaa.txt
//│  bbb.txt
//│
//└─dir
//        ccc.txt
//        ddd.txt

try (final var stream = Files.list(dir1)) {
    stream.forEach(System.out::println);

    // Result
    // ↓
    //D:\java-work\aaa.txt
    //D:\java-work\bbb.txt
    //D:\java-work\dir
}

try (final var stream = Files.list(dir2)) {
    stream.forEach(System.out::println);

    // Result
    // ↓
    //D:\java-work\dir\ccc.txt
    //D:\java-work\dir\ddd.txt
}

final var file = Path.of("D:", "java-work", "aaa.txt");
System.out.println(file); // D:\java-work\aaa.txt

Files.createFile(file);
System.out.println(Files.isRegularFile(file)); // true

try (var _ = Files.list(file)) {
    System.out.println("No errors");
} catch (NotDirectoryException e) {
    System.out.println("NotDirectoryException!");
}

// Result
// ↓
//NotDirectoryException!

static long mismatch (Path path, Path path2)

查找并返回两个文件内容中第一个不匹配的字节的位置，如果没有不匹配则返回 -1L。 (机器翻译)

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

final var file1 = Path.of("D:", "java-work", "aaa1.txt");
final var file2 = Path.of("D:", "java-work", "aaa2.txt");
final var file3 = Path.of("D:", "java-work", "aaa3.txt");
final var file4 = Path.of("D:", "java-work", "aaa4.txt");
final var file5 = Path.of("D:", "java-work", "aaa5.txt");
final var file6 = Path.of("D:", "java-work", "aaa6.txt");

Files.write(target, new byte[]{0, 1, 2});

Files.write(file1, new byte[]{0, 1, 2});
Files.write(file2, new byte[]{0, 1, 102});
Files.write(file3, new byte[]{0, 101, 102});
Files.write(file4, new byte[]{100, 101, 102});
Files.write(file5, new byte[]{});
Files.write(file6, new byte[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9});

// --- PowerShell ---
//PS D:\java-work> ls -Name
//aaa1.txt
//aaa2.txt
//aaa3.txt
//aaa4.txt
//aaa5.txt
//aaa6.txt
//target.txt

System.out.println(Arrays.toString(Files.readAllBytes(target))); // [0, 1, 2]

System.out.println(Arrays.toString(Files.readAllBytes(file1))); // [0, 1, 2]
System.out.println(Files.mismatch(target, file1)); // -1

System.out.println(Arrays.toString(Files.readAllBytes(file2))); // [0, 1, 102]
System.out.println(Files.mismatch(target, file2)); // 2

System.out.println(Arrays.toString(Files.readAllBytes(file3))); // [0, 101, 102]
System.out.println(Files.mismatch(target, file3)); // 1

System.out.println(Arrays.toString(Files.readAllBytes(file4))); // [100, 101, 102]
System.out.println(Files.mismatch(target, file4)); // 0

System.out.println(Arrays.toString(Files.readAllBytes(file5))); // []
System.out.println(Files.mismatch(target, file5)); // 0

final var ret = Files.readAllBytes(file6);
System.out.println(Arrays.toString(ret)); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
System.out.println(Files.mismatch(target, file6)); // 3

static Path move (Path source, Path target, CopyOption... options)

将文件移动或重命名为目标文件。 (机器翻译)

final var source = Path.of("D:", "java-work", "source.txt");
System.out.println(source); // D:\java-work\source.txt

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

Files.writeString(source, "abcd");

System.out.println(Files.exists(source)); // true
System.out.println(Files.exists(target)); // false

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property Mode, Length, Name
//
//Mode  Length Name
//----  ------ ----
//-a---      4 source.txt

System.out.println(Files.move(source, target)); // D:\java-work\target.txt

System.out.println(Files.exists(source)); // false
System.out.println(Files.exists(target)); // true

System.out.println(Files.readString(target)); // abcd

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property Mode, Length, Name
//
//Mode  Length Name
//----  ------ ----
//-a---      4 target.txt

final var source = Path.of("D:", "java-work", "source-dir");
System.out.println(source); // D:\java-work\source-dir

final var target = Path.of("D:", "java-work", "target-dir");
System.out.println(target); // D:\java-work\target-dir

Files.createDirectory(source);
Files.createFile(source.resolve(Path.of("aaa.txt")));
Files.createFile(source.resolve(Path.of("bbb.txt")));

System.out.println(Files.exists(source)); // true
System.out.println(Files.exists(target)); // false

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//└─source-dir
//        aaa.txt
//        bbb.txt

System.out.println(Files.move(source, target)); // D:\java-work\target-dir

System.out.println(Files.exists(source)); // false
System.out.println(Files.exists(target)); // true

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//└─target-dir
//        aaa.txt
//        bbb.txt

final var source = Path.of("D:", "java-work", "source.txt");
System.out.println(source); // D:\java-work\source.txt

Files.createFile(source);
System.out.println(Files.exists(source)); // true

// --- PowerShell ---
//PS D:\java-work> ls -Name
//source.txt

System.out.println(Files.move(source, source)); // D:\java-work\source.txt

System.out.println(Files.exists(source)); // true

// --- PowerShell ---
//PS D:\java-work> ls -Name
//source.txt

final var source = Path.of("D:", "java-work", "source.txt");
System.out.println(source); // D:\java-work\source.txt

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

Files.createFile(source);
Files.createFile(target);

System.out.println(Files.exists(source)); // true
System.out.println(Files.exists(target)); // true

// --- PowerShell ---
//PS D:\java-work> ls -Name
//source.txt
//target.txt

try {
    Files.move(source, target);
} catch (FileAlreadyExistsException e) {
    System.out.println("FileAlreadyExistsException!");
}

// Result
// ↓
//FileAlreadyExistsException!

// An example of moving a file to a different FileStore.

final var source = Path.of("D:", "java-work", "source.txt");
System.out.println(source); // D:\java-work\source.txt

final var target = Path.of("R:", "java-work", "target.txt");
System.out.println(target); // R:\java-work\target.txt

Files.createFile(source);

System.out.println(Files.exists(source)); // true
System.out.println(Files.exists(target)); // false

System.out.println(Files.move(source, target)); // R:\java-work\target.txt

System.out.println(Files.exists(source)); // false
System.out.println(Files.exists(target)); // true

// An example of moving a directory to a different FileStore.

final var source = Path.of("D:", "java-work", "source-dir");
System.out.println(source); // D:\java-work\source-dir

final var target = Path.of("R:", "java-work", "target-dir");
System.out.println(target); // R:\java-work\target-dir

Files.createDirectory(source);
Files.createFile(source.resolve(Path.of("aaa.txt")));

System.out.println(Files.exists(source)); // true
System.out.println(Files.exists(target)); // false

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//└─source-dir
//        aaa.txt

try {
    Files.move(source, target);
} catch (DirectoryNotEmptyException e) {
    System.out.println("DirectoryNotEmptyException!");
}

// Result
// ↓
//DirectoryNotEmptyException!

static BufferedReader newBufferedReader (Path path)

打开一个文件进行读取，返回一个 BufferedReader 以有效的方式从文件中读取文本。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.writeString(path, """
        abcd
        XYZ
        12345
        """);

try (final var reader = Files.newBufferedReader(path)) {
    System.out.println(reader.readLine()); // abcd
    System.out.println(reader.readLine()); // XYZ
    System.out.println(reader.readLine()); // 12345
}

static BufferedReader newBufferedReader (Path path, Charset cs)

打开一个文件进行读取，返回一个可用于以有效方式从文件中读取文本的 BufferedReader。 (机器翻译)

Please see also : newBufferedReader(Path path)

final var utf8 = Path.of("D:", "java-work", "aaa.txt");
System.out.println(utf8); // D:\java-work\aaa.txt

Files.writeString(utf8, "〇△□×", StandardCharsets.UTF_8);

try (final var reader = Files.newBufferedReader(utf8, StandardCharsets.UTF_8)) {
    System.out.println(reader.readLine()); // 〇△□×
}

try (final var reader = Files.newBufferedReader(utf8, Charset.forName("Shift_JIS"))) {
    reader.readLine();
} catch (MalformedInputException e) {
    System.out.println("MalformedInputException!");
}

// Result
// ↓
//MalformedInputException!

final var sjis = Path.of("D:", "java-work", "aaa.txt");
System.out.println(sjis); // D:\java-work\aaa.txt

Files.writeString(sjis, "〇△□×", Charset.forName("Shift_JIS"));

try (final var reader = Files.newBufferedReader(sjis, Charset.forName("Shift_JIS"))) {
    System.out.println(reader.readLine()); // 〇△□×
}

try (final var reader = Files.newBufferedReader(sjis, StandardCharsets.UTF_8)) {
    reader.readLine();
} catch (MalformedInputException e) {
    System.out.println("MalformedInputException!");
}

// Result
// ↓
//MalformedInputException!

static BufferedWriter newBufferedWriter (Path path, Charset cs, OpenOption... options)

打开或创建一个文件进行写入，返回一个可用于以有效方式将文本写入文件的 BufferedWriter。 (机器翻译)

final var sjis = Path.of("D:", "java-work", "aaa.txt");
System.out.println(sjis); // D:\java-work\aaa.txt

try (final var writer = Files.newBufferedWriter(sjis, Charset.forName("Shift_JIS"))) {
    writer.write("〇△□×");
}

System.out.println(Files.readString(sjis, Charset.forName("Shift_JIS"))); // 〇△□×

try {
    Files.readString(sjis, StandardCharsets.UTF_8);
} catch (MalformedInputException e) {
    System.out.println("MalformedInputException!");
}

// Result
// ↓
//MalformedInputException!

static BufferedWriter newBufferedWriter (Path path, OpenOption... options)

打开或创建一个文件进行写入，返回一个 BufferedWriter 以有效的方式将文本写入文件。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

try (final var writer = Files.newBufferedWriter(path)) {
    writer.write("abcd");
    writer.newLine();

    writer.write("XYZ");
    writer.newLine();
}

final var str = Files.readString(path);
System.out.print(str);

// Result
// ↓
//abcd
//XYZ

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

try (final var writer = Files.newBufferedWriter(path)) {
    writer.write("abcd");
}

System.out.println(Files.readString(path)); // abcd

try (final var writer = Files.newBufferedWriter(path)) {
    writer.write("XYZ");
}

System.out.println(Files.readString(path)); // XYZ

try (final var writer = Files.newBufferedWriter(path, StandardOpenOption.APPEND)) {
    writer.write("1234");
}

System.out.println(Files.readString(path)); // XYZ1234

static SeekableByteChannel newByteChannel (Path path, OpenOption... options)

打开或创建一个文件，返回一个可寻址的字节通道来访问该文件。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.data");
System.out.println(path);
System.out.println(Files.notExists(path)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

try (final var channel = Files.newByteChannel(path,
        StandardOpenOption.CREATE_NEW, StandardOpenOption.WRITE)) {
    final var src = ByteBuffer.wrap(new byte[]{10, 20, 30});
    System.out.println(Arrays.toString(src.array())); // [10, 20, 30]
    System.out.println(channel.write(src)); // 3
}

System.out.println(Arrays.toString(Files.readAllBytes(path))); // [10, 20, 30]

try (final var channel = Files.newByteChannel(path, StandardOpenOption.READ)) {
    final var dst = ByteBuffer.allocate(3);
    System.out.println(channel.read(dst)); // 3
    System.out.println(Arrays.toString(dst.array())); // [10, 20, 30]
}

static SeekableByteChannel newByteChannel (Path path, Set<? extends OpenOption> options, FileAttribute<?>... attrs)

打开或创建一个文件，返回一个可寻址的字节通道来访问该文件。 (机器翻译)

Please see below links.

newByteChannel(Path path, OpenOption... options)
An example of FileAttribute : createFile(Path path, FileAttribute<?>... attrs)

static DirectoryStream<Path> newDirectoryStream (Path dir)

打开一个目录，返回一个 DirectoryStream 来迭代目录中的所有条目。 (机器翻译)

final var dir = Path.of("D:", "java-work");
System.out.println(dir); // D:\java-work

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//    aaa.txt
//    bbb.txt
//    ccc.txt

try (final var stream = Files.newDirectoryStream(dir)) {
    for (final var path : stream) {
        System.out.println(path);
    }
}

// Result
// ↓
//D:\java-work\aaa.txt
//D:\java-work\bbb.txt
//D:\java-work\ccc.txt

final var dir = Path.of("D:", "java-work");
System.out.println(dir); // D:\java-work

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//│  aaa1.txt
//│  aaa2.txt
//│
//└─dir
//        bbb1.txt
//        bbb2.txt

try (final var stream = Files.newDirectoryStream(dir)) {
    for (final var path : stream) {
        System.out.println(path);
    }
}

// Result
// ↓
//D:\java-work\aaa1.txt
//D:\java-work\aaa2.txt
//D:\java-work\dir

final var nonExistentPath = Path.of("D:", "java-work", "xxx");
System.out.println(nonExistentPath); // D:\java-work\xxx

System.out.println(Files.notExists(nonExistentPath)); // true

try (var _ = Files.newDirectoryStream(nonExistentPath)) {
    System.out.println("No errors");
} catch (NoSuchFileException e) {
    System.out.println("NoSuchFileException!");
}

// Result
// ↓
//NoSuchFileException!

static DirectoryStream<Path> newDirectoryStream (Path dir, String glob)

打开一个目录，返回一个 DirectoryStream 来迭代目录中的条目。 (机器翻译)

Please see also : newDirectoryStream(Path dir)

final var dir = Path.of("D:", "java-work");
System.out.println(dir); // D:\java-work

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//    aaa.txt
//    bbb.txt
//    Book.java
//    Page.java

try (final var stream = Files.newDirectoryStream(dir, "*")) {
    for (final var file : stream) {
        System.out.println(file);
    }
}

// Result
// ↓
//D:\java-work\aaa.txt
//D:\java-work\bbb.txt
//D:\java-work\Book.java
//D:\java-work\Page.java

try (final var stream = Files.newDirectoryStream(dir, "*.java")) {
    for (final var file : stream) {
        System.out.println(file);
    }
}

// Result
// ↓
//D:\java-work\Book.java
//D:\java-work\Page.java

try (final var stream = Files.newDirectoryStream(dir, "b*")) {
    for (final var file : stream) {
        System.out.println(file);
    }
}

// Result
// ↓
//D:\java-work\bbb.txt
//D:\java-work\Book.java

static DirectoryStream<Path> newDirectoryStream (Path dir, DirectoryStream.Filter<? super Path> filter)

打开一个目录，返回一个 DirectoryStream 来迭代目录中的条目。 (机器翻译)

Please see also : newDirectoryStream(Path dir)

final var dir = Path.of("D:", "java-work");
System.out.println(dir); // D:\java-work

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//    aaa.txt
//    bbb.txt
//    Book.java
//    Page.java

try (final var stream = Files.newDirectoryStream(dir, (_) -> true)) {
    for (final var path : stream) {
        System.out.println(path);
    }
}

// Result
// ↓
//D:\java-work\aaa.txt
//D:\java-work\bbb.txt
//D:\java-work\Book.java
//D:\java-work\Page.java

try (final var stream = Files.newDirectoryStream(dir, (path) -> path.toString().endsWith(".java"))) {
    for (final var path : stream) {
        System.out.println(path);
    }
}

// Result
// ↓
//D:\java-work\Book.java
//D:\java-work\Page.java

static InputStream newInputStream (Path path, OpenOption... options)

打开一个文件，返回一个输入流来从文件中读取。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.write(path, new byte[]{10, 20, 30});

// --- PowerShell ---
//PS D:\java-work> ls -Name
//aaa.txt

try (final var inputStream = Files.newInputStream(path)) {
    final var bytes = inputStream.readAllBytes();
    System.out.println(Arrays.toString(bytes)); // [10, 20, 30]
}

final var target = Path.of("D:", "java-work", "aaa.txt");
System.out.println(target); // D:\java-work\aaa.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.write(target, new byte[]{10, 20, 30});
Files.createSymbolicLink(link, target);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//-a---  ...        3 aaa.txt
//la---  ...        0 link.txt -> D:\java-work\aaa.txt

try (final var inputStream = Files.newInputStream(target)) {
    final var bytes = inputStream.readAllBytes();
    System.out.println(Arrays.toString(bytes)); // [10, 20, 30]
}

try (final var inputStream = Files.newInputStream(link)) {
    final var bytes = inputStream.readAllBytes();
    System.out.println(Arrays.toString(bytes)); // [10, 20, 30]
}

try (var _ = Files.newInputStream(link, LinkOption.NOFOLLOW_LINKS)) {
    System.out.println("No errors");
} catch (IOException e) {
    System.out.println(e);
}

// Result
// ↓
//java.io.IOException: File is symbolic link

static OutputStream newOutputStream (Path path, OpenOption... options)

打开或创建一个文件，返回可用于将字节写入文件的输出流。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

try (final var outputStream = Files.newOutputStream(path)) {
    outputStream.write(10);
    outputStream.write(20);
    outputStream.write(new byte[]{30, 40, 50});
}

final var bytes = Files.readAllBytes(path);
System.out.println(Arrays.toString(bytes)); // [10, 20, 30, 40, 50]

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

try (final var outputStream = Files.newOutputStream(path)) {
    outputStream.write(10);
    outputStream.write(20);
}

System.out.println(Arrays.toString(Files.readAllBytes(path))); // [10, 20]

try (final var outputStream = Files.newOutputStream(path)) {
    outputStream.write(30);
    outputStream.write(40);
}

System.out.println(Arrays.toString(Files.readAllBytes(path))); // [30, 40]

try (final var outputStream = Files.newOutputStream(
        path, StandardOpenOption.APPEND)) {
    outputStream.write(50);
    outputStream.write(60);
}

System.out.println(Arrays.toString(Files.readAllBytes(path))); // [30, 40, 50, 60]

static boolean notExists (Path path, LinkOption... options)

测试此路径所在的文件是否不存在。 (机器翻译)

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir

final var file = Path.of("D:", "java-work", "aaa.txt");
System.out.println(file); // D:\java-work\aaa.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

final var nonExistentPath = Path.of("D:", "java-work", "xxx");
System.out.println(nonExistentPath); // D:\java-work\xxx

Files.createDirectory(dir);
Files.createFile(file);
Files.createSymbolicLink(link, nonExistentPath);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//d----  ...          dir
//-a---  ...        0 aaa.txt
//la---  ...        0 link.txt -> D:\java-work\xxx

System.out.println(Files.isDirectory(dir)); // true
System.out.println(Files.notExists(dir)); // false

System.out.println(Files.isRegularFile(file)); // true
System.out.println(Files.notExists(file)); // false

System.out.println(Files.isSymbolicLink(link)); // true
System.out.println(Files.notExists(link)); // true
System.out.println(Files.notExists(link, LinkOption.NOFOLLOW_LINKS)); // false

System.out.println(Files.notExists(nonExistentPath)); // true

static String probeContentType (Path path)

探测文件的内容类型。 (机器翻译)

// --- PowerShell ---
//PS D:\java-work> ls -Name
//image.png
//index.html
//text.txt
//unknown.abc

final var imageFile = Path.of("D:", "java-work", "image.png");
System.out.println(Files.probeContentType(imageFile)); // "image/png"

final var htmlFile = Path.of("D:", "java-work", "index.html");
System.out.println(Files.probeContentType(htmlFile)); // "text/html"

final var textFile = Path.of("D:", "java-work", "text.txt");
System.out.println(Files.probeContentType(textFile)); // "text/plain"

final var unknownFile = Path.of("D:", "java-work", "unknown.abc");
System.out.println(Files.probeContentType(unknownFile)); // null

static byte[] readAllBytes (Path path)

从文件读取所有字节。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.write(path, new byte[]{10, 20, 30});

// --- PowerShell ---
//PS D:\java-work> ls -Name
//aaa.txt

final var ret = Files.readAllBytes(path);
System.out.println(Arrays.toString(ret)); // [10, 20, 30]

static List<String> readAllLines (Path path)

从文件读取所有行。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.writeString(path, """
        abcd
        XYZ
        12345
        """);

// --- PowerShell ---
//PS D:\java-work> ls -Name
//aaa.txt

final var ret = Files.readAllLines(path);
System.out.println(ret); // [abcd, XYZ, 12345]

static List<String> readAllLines (Path path, Charset cs)

从文件读取所有行。 (机器翻译)

Please see also : readAllLines(Path path)

final var utf8 = Path.of("D:", "java-work", "aaa.txt");
System.out.println(utf8); // D:\java-work\aaa.txt

Files.writeString(utf8, """
        abcd
        〇△□×
        """, StandardCharsets.UTF_8);

// --- PowerShell ---
//PS D:\java-work> ls -Name
//aaa.txt

final var lines = Files.readAllLines(utf8, StandardCharsets.UTF_8);
System.out.println(lines); // [abcd, 〇△□×]

try {
    Files.readAllLines(utf8, Charset.forName("Shift_JIS"));
} catch (MalformedInputException e) {
    System.out.println("MalformedInputException!");
}

// Result
// ↓
//MalformedInputException!

final var sjis = Path.of("D:", "java-work", "aaa.txt");
System.out.println(sjis); // D:\java-work\aaa.txt

Files.writeString(sjis, """
        abcd
        〇△□×
        """, Charset.forName("Shift_JIS"));

// --- PowerShell ---
//PS D:\java-work> ls -Name
//aaa.txt

final var lines = Files.readAllLines(sjis, Charset.forName("Shift_JIS"));
System.out.println(lines); // [abcd, 〇△□×]

try {
    Files.readAllLines(sjis, StandardCharsets.UTF_8);
} catch (MalformedInputException e) {
    System.out.println("MalformedInputException!");
}

// Result
// ↓
//MalformedInputException!

static <A extends BasicFileAttributes> A readAttributes (Path path, Class<A> type, LinkOption... options)

通过批量操作读取文件的属性。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.writeString(path, "abcd");

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property Mode, Length, Name
//
//Mode  Length Name
//----  ------ ----
//-a---      4 aaa.txt

final var attrs = Files.readAttributes(path, BasicFileAttributes.class);

System.out.println(attrs.isDirectory()); // false
System.out.println(attrs.isRegularFile()); // true
System.out.println(attrs.size()); // 4

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir

Files.createDirectory(dir);

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//d---- dir

final var attrs = Files.readAttributes(dir, BasicFileAttributes.class);

System.out.println(attrs.isDirectory()); // true
System.out.println(attrs.isRegularFile()); // false

final var target = Path.of("D:", "java-work", "aaa.txt");
System.out.println(target); // D:\java-work\aaa.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.createFile(target);
Files.createSymbolicLink(link, target);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//-a---  ...        0 aaa.txt
//la---  ...        0 link.txt -> D:\java-work\aaa.txt

final var attrs1 = Files.readAttributes(link, BasicFileAttributes.class);
System.out.println(attrs1.isSymbolicLink()); // false

final var attrs2 = Files.readAttributes(link,
        BasicFileAttributes.class, LinkOption.NOFOLLOW_LINKS);
System.out.println(attrs2.isSymbolicLink()); // true

final var readOnlyFile = Path.of("D:", "java-work", "read-only.txt");
System.out.println(readOnlyFile); // D:\java-work\read-only.txt

final var hiddenFile = Path.of("D:", "java-work", "hidden.txt");
System.out.println(hiddenFile); // D:\java-work\hidden.txt

Files.createFile(readOnlyFile);
Files.setAttribute(readOnlyFile, "dos:readonly", true);

Files.createFile(hiddenFile);
Files.setAttribute(hiddenFile, "dos:hidden", true);

// --- PowerShell ---
//PS D:\java-work> ls -Force | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//-a-h- hidden.txt
//-ar-- read-only.txt

final var attrs1 = Files.readAttributes(readOnlyFile, DosFileAttributes.class);

System.out.println(attrs1.isHidden()); // false
System.out.println(attrs1.isReadOnly()); // true

final var attrs2 = Files.readAttributes(hiddenFile, DosFileAttributes.class);

System.out.println(attrs2.isHidden()); // true
System.out.println(attrs2.isReadOnly()); // false

static Map<String,Object> readAttributes (Path path, String attributes, LinkOption... options)

通过批量操作读取一组文件属性。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.createFile(path);

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//-a--- aaa.txt

final var file = Path.of("D:", "java-work", "aaa.txt");
final var attrs = Files.readAttributes(file, "*");

//{lastAccessTime=2024-10-19T07:19:25.3063571Z,
// lastModifiedTime=2024-10-19T07:19:25.3063571Z,
// size=0, creationTime=2024-10-19T07:14:47.356487Z,
// isSymbolicLink=false, isRegularFile=true, fileKey=null,
// isOther=false, isDirectory=false}
System.out.println(attrs);

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir

Files.createDirectory(dir);

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//d---- dir

final var attrs = Files.readAttributes(dir, "isRegularFile,isDirectory");
System.out.println(attrs); // {isRegularFile=false, isDirectory=true}

final var target = Path.of("D:", "java-work", "aaa.txt");
System.out.println(target); // D:\java-work\aaa.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.createFile(target);
Files.createSymbolicLink(link, target);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//-a---  ...        0 aaa.txt
//la---  ...        0 link.txt -> D:\java-work\aaa.txt

final var attrs1 = Files.readAttributes(link, "isRegularFile,isSymbolicLink");
System.out.println(attrs1); // {isSymbolicLink=false, isRegularFile=true}

final var attrs2 = Files.readAttributes(link,
        "isRegularFile,isSymbolicLink", LinkOption.NOFOLLOW_LINKS);
System.out.println(attrs2); // {isSymbolicLink=true, isRegularFile=false}

final var readOnlyFile = Path.of("D:", "java-work", "read-only.txt");
System.out.println(readOnlyFile); // D:\java-work\read-only.txt

final var hiddenFile = Path.of("D:", "java-work", "hidden.txt");
System.out.println(hiddenFile); // D:\java-work\hidden.txt

Files.createFile(readOnlyFile);
Files.setAttribute(readOnlyFile, "dos:readonly", true);

Files.createFile(hiddenFile);
Files.setAttribute(hiddenFile, "dos:hidden", true);

// --- PowerShell ---
//PS D:\java-work> ls -Force | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//-a-h- hidden.txt
//-ar-- read-only.txt

final var attrs1 = Files.readAttributes(
        readOnlyFile, "dos:isRegularFile,hidden,readonly");
System.out.println(attrs1); // {readonly=true, hidden=false, isRegularFile=true}

final var attrs2 = Files.readAttributes(
        hiddenFile, "dos:isRegularFile,hidden,readonly");
System.out.println(attrs2); // {readonly=false, hidden=true, isRegularFile=true}

static String readString (Path path)

将文件中的所有内容读入字符串，使用 UTF-8 字符集将字节解码为字符。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.writeString(path, """
        abcd
        XYZ
        12345
        """);

// --- PowerShell ---
//PS D:\java-work> ls -Name
//aaa.txt

final var ret = Files.readString(path);
System.out.println(ret);

// Result
// ↓
//abcd
//XYZ
//12345

static String readString (Path path, Charset cs)

将文件中的所有字符读入字符串，使用指定的字符集将字节解码为字符。 (机器翻译)

Please see also : readString(Path path)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.writeString(path, "〇△□×", Charset.forName("Shift_JIS"));

// --- PowerShell ---
//PS D:\java-work> ls -Name
//aaa.txt

System.out.println(Files.readString(path, Charset.forName("Shift_JIS"))); // 〇△□×

try {
    Files.readString(path, StandardCharsets.UTF_8);
} catch (MalformedInputException e) {
    System.out.println("MalformedInputException!");
}

// Result
// ↓
//MalformedInputException!

static Path readSymbolicLink (Path link)

读取符号链接的目标（可选操作）。 (机器翻译)

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.createFile(target);
Files.createSymbolicLink(link, target);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//la---  ...        0 link.txt -> D:\java-work\target.txt
//-a---  ...        0 target.txt

System.out.println(Files.isRegularFile(link)); // true
System.out.println(Files.isSymbolicLink(link)); // true
System.out.println(Files.readSymbolicLink(link)); // aaa.txt

try {
    System.out.println(Files.isRegularFile(target)); // true
    System.out.println(Files.isSymbolicLink(target)); // false
    Files.readSymbolicLink(target);

} catch (NotLinkException e) {
    System.out.println("NotLinkException!");
}

// Result
// ↓
//NotLinkException!

static Path setAttribute (Path path, String attribute, Object value, LinkOption... options)

设置文件属性的值。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.createFile(path);
System.out.println(Files.isHidden(path)); // false

// --- PowerShell ---
//PS D:\java-work> ls -Force | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//-a--- aaa.txt

Files.setAttribute(path, "dos:hidden", true);
System.out.println(Files.isHidden(path)); // true

// --- PowerShell ---
//PS D:\java-work> ls -Force | Format-Table -Property Mode, Name
//
//Mode  Name
//----  ----
//-a-h- aaa.txt

final var target = Path.of("D:", "java-work", "target.txt");
System.out.println(target); // D:\java-work\target.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.createFile(target);
Files.createSymbolicLink(link, target);

System.out.println(Files.isHidden(target)); // false

// --- PowerShell ---
//PS D:\java-work> ls -Force
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//la---  ...        0 link.txt -> D:\java-work\target.txt
//-a---  ...        0 target.txt

Files.setAttribute(link, "dos:hidden", true);
System.out.println(Files.isHidden(target)); // true

// --- PowerShell ---
//PS D:\java-work> ls -Force
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//la---  ...        0 link.txt -> D:\java-work\target.txt
//-a-h-  ...        0 target.txt

Files.setAttribute(link, "dos:hidden", true, LinkOption.NOFOLLOW_LINKS);
System.out.println(Files.isHidden(target)); // true

// --- PowerShell ---
//PS D:\java-work> ls -Force
//...
//Mode   ...   Length Name
//----   ...   ------ ----
//la-h-  ...        0 link.txt -> D:\java-work\target.txt
//-a-h-  ...        0 target.txt

static Path setLastModifiedTime (Path path, FileTime time)

更新文件的最后修改时间属性。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.createFile(path);

final var zoneId = ZoneId.systemDefault();
System.out.println(zoneId); // Asia/Tokyo

final var ret = Files.setLastModifiedTime(path, FileTime.from(
        ZonedDateTime.of(2100, 1, 1, 0, 0, 0, 0, zoneId).toInstant()));
System.out.println(ret); // D:\java-work\aaa.txt

// --- PowerShell ---
//PS D:\java-work> ls | Format-Table -Property LastWriteTime, Name
//
//LastWriteTime      Name
//-------------      ----
//2100/01/01 0:00:00 aaa.txt

// FileTime is UTC.
final var fileTime = Files.getLastModifiedTime(path);
System.out.println(fileTime); // 2099-12-31T15:00:00Z

final var zonedDateTime = ZonedDateTime.ofInstant(fileTime.toInstant(), zoneId);
System.out.println(zonedDateTime); // 2100-01-01T00:00+09:00[Asia/Tokyo]

final var target = Path.of("D:", "java-work", "aaa.txt");
System.out.println(target); // D:\java-work\aaa.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

final var zoneId = ZoneId.systemDefault();
System.out.println(zoneId); // Asia/Tokyo

final var zonedDateTime = ZonedDateTime.of(2100, 1, 1, 0, 0, 0, 0, zoneId);
System.out.println(zonedDateTime); // 2100-01-01T00:00+09:00[Asia/Tokyo]

Files.createFile(target);
Files.setLastModifiedTime(target, FileTime.from(zonedDateTime.toInstant()));

Files.createSymbolicLink(link, target);

// --- PowerShell ---
//PS D:\java-work> ls
//...
//Mode                 LastWriteTime         Length Name
//----                 -------------         ------ ----
//-a---          2100/01/01     0:00              0 aaa.txt
//la---          2024/10/19    16:31              0 link.txt -> D:\java-work\aaa.txt

final var ret1 = Files.getLastModifiedTime(link);
System.out.println(ret1); // 2099-12-31T15:00:00Z

final var ret2 = Files.getLastModifiedTime(link, LinkOption.NOFOLLOW_LINKS);
System.out.println(ret2); // 2024-10-19T07:31:55.9393338Z

static Path setOwner (Path path, UserPrincipal owner)

更新文件所有者。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt

Files.createFile(path);

final var service = path.getFileSystem().getUserPrincipalLookupService();
final var newOwner = service.lookupPrincipalByName("test-user");

final var ret1 = Files.setOwner(path, newOwner);
System.out.println(ret1); // D:\java-work\aaa.txt

// --- PowerShell ---
//PS D:\java-work> Get-Acl .\aaa.txt
//...
//Path    Owner           Access
//----    -----           ------
//aaa.txt MY-PC\test-user BUILTIN\Administrators Allow  FullControl…

final var ret2 = Files.getOwner(path);
System.out.println(ret2); // MY-PC\test-user (User)

final var target = Path.of("D:", "java-work", "aaa.txt");
System.out.println(target); // D:\java-work\aaa.txt

final var link = Path.of("D:", "java-work", "link.txt");
System.out.println(link); // D:\java-work\link.txt

Files.createSymbolicLink(link, target);

// --- PowerShell ---
//PS D:\java-work> ls | Get-Acl
//..
//Path     Owner                    Access
//----     -----                    ------
//aaa.txt  MY-PC\test-user          BUILTIN\Administrators Allow  FullControl…
//link.txt BUILTIN\Administrators   BUILTIN\Administrators Allow  FullControl…

final var ret1 = Files.getOwner(link);
System.out.println(ret1); // MY-PC\test-user (User)

final var ret2 = Files.getOwner(link, LinkOption.NOFOLLOW_LINKS);
System.out.println(ret2); // BUILTIN\Administrators (Alias)

static Path setPosixFilePermissions (Path path, Set<PosixFilePermission> perms)

设置文件的 POSIX 权限。 (机器翻译)

The following code runs on Linux.

System.out.println(System.getProperty("os.name")); // Linux

// --- Linux Terminal ---
//$ ls -l sample.sh
//-rw-rw-r-- 1 xxxx xxxx 0 ... sample.sh

final var path = Path.of("sample.sh");

final var permissions = Files.getPosixFilePermissions(path);
System.out.println(PosixFilePermissions.toString(permissions)); // rw-rw-r--

final var newPermissions = PosixFilePermissions.fromString("rwxr-xr--");

final var ret = Files.setPosixFilePermissions(path, newPermissions);
System.out.println(ret); // sample.sh

// --- Linux Terminal ---
//$ ls -l sample.sh
//-rwxr-xr-- 1 xxxx xxxx 0 ... sample.sh

static long size (Path path)

返回文件的大小（以字节为单位）。 (机器翻译)

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//│  aaa.txt
//│  bbb.txt
//│
//└─dir
//        ccc.txt
//
//PS D:\java-work> ls -Recurse
//
//    Directory: D:\java-work
//
//Mode   ...   Length Name
//----   ...   ------ ----
//d----  ...          dir
//-a---  ...        5 aaa.txt
//-a---  ...     1000 bbb.txt
//
//    Directory: D:\java-work\dir
//
//Mode   ...   Length Name
//----   ...   ------ ----
//-a---  ...       12 ccc.txt


final var file1 = Path.of("D:", "java-work", "aaa.txt");
System.out.println(file1); // D:\java-work\aaa.txt
System.out.println(Files.size(file1)); // 5

final var file2 = Path.of("D:", "java-work", "bbb.txt");
System.out.println(file2); // D:\java-work\bbb.txt
System.out.println(Files.size(file2)); // 1000

final var dir = Path.of("D:", "java-work", "dir");
System.out.println(dir); // D:\java-work\dir
System.out.println(Files.size(dir)); // 0

final var nonExistentPath = Path.of("D:", "java-work", "xxx");
System.out.println(nonExistentPath); // D:\java-work\xxx
System.out.println(Files.notExists(nonExistentPath)); // true

try {
    Files.size(nonExistentPath);
} catch (NoSuchFileException e) {
    System.out.println("NoSuchFileException!");
}

// Result
// ↓
//NoSuchFileException!

static Stream<Path> walk (Path start, int maxDepth, FileVisitOption... options)

通过遍历以给定起始文件为根的文件树，返回一个用 Path 延迟填充的 Stream。 (机器翻译)

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//│  aaa.txt
//│  bbb.txt
//│
//├─dir1
//│  │  ccc.txt
//│  │  ddd.txt
//│  │
//│  └─dir1-2
//│          eee.txt
//│          fff.txt
//│
//└─dir2
//        ggg.txt
//        hhh.txt

final var start = Path.of("D:", "java-work");
System.out.println(start); // D:\java-work

System.out.println("maxDepth : 3");
try (final var stream = Files.walk(start, 3)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//maxDepth : 3
//D:\java-work
//D:\java-work\aaa.txt
//D:\java-work\bbb.txt
//D:\java-work\dir1
//D:\java-work\dir1\ccc.txt
//D:\java-work\dir1\ddd.txt
//D:\java-work\dir1\dir1-2
//D:\java-work\dir1\dir1-2\eee.txt
//D:\java-work\dir1\dir1-2\fff.txt
//D:\java-work\dir2
//D:\java-work\dir2\ggg.txt
//D:\java-work\dir2\hhh.txt

System.out.println("maxDepth : 2");
try (final var stream = Files.walk(start, 2)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//maxDepth : 2
//D:\java-work
//D:\java-work\aaa.txt
//D:\java-work\bbb.txt
//D:\java-work\dir1
//D:\java-work\dir1\ccc.txt
//D:\java-work\dir1\ddd.txt
//D:\java-work\dir1\dir1-2
//D:\java-work\dir2
//D:\java-work\dir2\ggg.txt
//D:\java-work\dir2\hhh.txt

System.out.println("maxDepth : 1");
try (final var stream = Files.walk(start, 1)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//maxDepth : 1
//D:\java-work
//D:\java-work\aaa.txt
//D:\java-work\bbb.txt
//D:\java-work\dir1
//D:\java-work\dir2

System.out.println("maxDepth : 0");
try (final var stream = Files.walk(start, 0)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//maxDepth : 0
//D:\java-work

static Stream<Path> walk (Path start, FileVisitOption... options)

通过遍历以给定起始文件为根的文件树，返回一个用 Path 延迟填充的 Stream。 (机器翻译)

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//│  aaa.txt
//│  bbb.txt
//│
//├─dir1
//│  │  ccc.txt
//│  │  ddd.txt
//│  │
//│  └─dir1-2
//│          eee.txt
//│          fff.txt
//│
//└─dir2
//        ggg.txt
//        hhh.txt

final var start = Path.of("D:", "java-work");
System.out.println(start); // D:\java-work

try (final var stream = Files.walk(start)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//D:\java-work
//D:\java-work\aaa.txt
//D:\java-work\bbb.txt
//D:\java-work\dir1
//D:\java-work\dir1\ccc.txt
//D:\java-work\dir1\ddd.txt
//D:\java-work\dir1\dir1-2
//D:\java-work\dir1\dir1-2\eee.txt
//D:\java-work\dir1\dir1-2\fff.txt
//D:\java-work\dir2
//D:\java-work\dir2\ggg.txt
//D:\java-work\dir2\hhh.txt

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//├─dir
//│      aaa.txt
//│      bbb.txt
//│
//└─link-dir
//        aaa.txt
//        bbb.txt
//
//PS D:\java-work> ls
//
//    Directory: D:\java-work
//
//Mode   ...   Length Name
//----   ...   ------ ----
//d----  ...          dir
//l----  ...          link-dir -> D:\java-work\dir

final var start = Path.of("D:", "java-work");
System.out.println(start); // D:\java-work

try (final var stream = Files.walk(start)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//D:\java-work
//D:\java-work\dir
//D:\java-work\dir\aaa.txt
//D:\java-work\dir\bbb.txt
//D:\java-work\link-dir

System.out.println("FileVisitOption : FOLLOW_LINKS");
try (final var stream = Files.walk(start, FileVisitOption.FOLLOW_LINKS)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//FileVisitOption : FOLLOW_LINKS
//D:\java-work
//D:\java-work\dir
//D:\java-work\dir\aaa.txt
//D:\java-work\dir\bbb.txt
//D:\java-work\link-dir
//D:\java-work\link-dir\aaa.txt
//D:\java-work\link-dir\bbb.txt

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//└─dir
//    │  aaa.txt
//    │  bbb.txt
//    │
//    └─link-parent-dir
//        │  aaa.txt
//        │  bbb.txt
//        │
//        └─link-parent-dir
//            │  aaa.txt
//            │  bbb.txt
// ...

// --- PowerShell ---
//PS D:\java-work> ls -Recurse
//
//    Directory: D:\java-work
//
//Mode   ...   Length Name
//----   ...   ------ ----
//d----  ...          dir
//
//    Directory: D:\java-work\dir
//
//Mode   ...   Length Name
//----   ...   ------ ----
//l----  ...          link-parent-dir -> D:\java-work\dir
//-a---  ...        0 aaa.txt
//-a---  ...        0 bbb.txt

// Symbolic links are circular.

final var start = Path.of("D:", "java-work");
System.out.println(start); // D:\java-work

try (final var stream = Files.walk(start)) {
    stream.forEach(System.out::println);
}

// Result
// ↓
//D:\java-work
//D:\java-work\dir
//D:\java-work\dir\aaa.txt
//D:\java-work\dir\bbb.txt
//D:\java-work\dir\link-parent-dir

System.out.println("FileVisitOption : FOLLOW_LINKS");
try (final var stream = Files.walk(start, FileVisitOption.FOLLOW_LINKS)) {
    stream.forEach(System.out::println);
} catch (UncheckedIOException e) {
    System.out.println(e);
}

// Result
// ↓
//FileVisitOption : FOLLOW_LINKS
//D:\java-work
//D:\java-work\dir
//D:\java-work\dir\aaa.txt
//D:\java-work\dir\bbb.txt
//java.io.UncheckedIOException: java.nio.file.FileSystemLoopException

final var start = Path.of("D:", "java-work", "xxx");
System.out.println(start); // D:\java-work\xxx
System.out.println(Files.notExists(start)); // true

try (var _ = Files.walk(start)) {
    System.out.println("No errors");
} catch (NoSuchFileException e) {
    System.out.println("NoSuchFileException!");
}

// Result
// ↓
//NoSuchFileException!

static Path walkFileTree (Path start, FileVisitor<? super Path> visitor)

遍历文件树。 (机器翻译)

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//│  aaa.txt
//│  bbb.txt
//│
//├─dir1
//│  │  ccc.txt
//│  │  ddd.txt
//│  │
//│  └─dir1-2
//│          eee.txt
//│          fff.txt
//│
//└─dir2
//        ggg.txt
//        hhh.txt

final var start = Path.of("D:", "java-work");
System.out.println(start); // D:\java-work

System.out.println("-- start --");
final var ret1 = Files.walkFileTree(start, new FileVisitor<>() {
    @Override
    public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
        System.out.println("preVisitDirectory : " + dir);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
        System.out.println("visitFile : " + file);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFileFailed(Path file, IOException exc) {
        System.out.println("visitFileFailed : " + file);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
        System.out.println("postVisitDirectory : " + dir);
        return FileVisitResult.CONTINUE;
    }
});

System.out.println("ret : " + ret1);

// Result
// ↓
//-- start --
//preVisitDirectory : D:\java-work
//visitFile : D:\java-work\aaa.txt
//visitFile : D:\java-work\bbb.txt
//preVisitDirectory : D:\java-work\dir1
//visitFile : D:\java-work\dir1\ccc.txt
//visitFile : D:\java-work\dir1\ddd.txt
//preVisitDirectory : D:\java-work\dir1\dir1-2
//visitFile : D:\java-work\dir1\dir1-2\eee.txt
//visitFile : D:\java-work\dir1\dir1-2\fff.txt
//postVisitDirectory : D:\java-work\dir1\dir1-2
//postVisitDirectory : D:\java-work\dir1
//preVisitDirectory : D:\java-work\dir2
//visitFile : D:\java-work\dir2\ggg.txt
//visitFile : D:\java-work\dir2\hhh.txt
//postVisitDirectory : D:\java-work\dir2
//postVisitDirectory : D:\java-work
//ret : D:\java-work

System.out.println("-- start --");
final var ret2 = Files.walkFileTree(start, new FileVisitor<>() {
    @Override
    public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
        System.out.println("preVisitDirectory : " + dir);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
        System.out.println("visitFile : " + file);
        if (Path.of("D:", "java-work", "aaa.txt").equals(file)) {
            return FileVisitResult.SKIP_SIBLINGS;
        }
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFileFailed(Path file, IOException exc) {
        System.out.println("visitFileFailed : " + file);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
        System.out.println("postVisitDirectory : " + dir);
        return FileVisitResult.CONTINUE;
    }
});

System.out.println("ret : " + ret2);

// Result
// ↓
//-- start --
//preVisitDirectory : D:\java-work
//visitFile : D:\java-work\aaa.txt
//postVisitDirectory : D:\java-work
//ret : D:\java-work

System.out.println("-- start --");
final var ret3 = Files.walkFileTree(start, new FileVisitor<>() {
    @Override
    public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
        System.out.println("preVisitDirectory : " + dir);
        if (Path.of("D:", "java-work", "dir1").equals(dir)) {
            return FileVisitResult.SKIP_SUBTREE;
        }

        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
        System.out.println("visitFile : " + file);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFileFailed(Path file, IOException exc) {
        System.out.println("visitFileFailed : " + file);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
        System.out.println("postVisitDirectory : " + dir);
        return FileVisitResult.CONTINUE;
    }
});

System.out.println("ret : " + ret3);

// Result
// ↓
//-- start --
//preVisitDirectory : D:\java-work
//visitFile : D:\java-work\aaa.txt
//visitFile : D:\java-work\bbb.txt
//preVisitDirectory : D:\java-work\dir1
//preVisitDirectory : D:\java-work\dir2
//visitFile : D:\java-work\dir2\ggg.txt
//visitFile : D:\java-work\dir2\hhh.txt
//postVisitDirectory : D:\java-work\dir2
//postVisitDirectory : D:\java-work
//ret : D:\java-work

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//├─dir1
//└─dir2
//        aaa.txt
//
//PS D:\java-work> ls | Get-Acl
//...
//Path Owner           Access
//---- -----           ------
//dir1 MY-PC\test-user BUILTIN\Administrators Deny  ReadData…
//dir2 MY-PC\test-user BUILTIN\Administrators Allow  FullControl…

// Intentional errors.

final var start = Path.of("D:", "java-work");
System.out.println(start); // D:\java-work

System.out.println("-- start --");
final var ret = Files.walkFileTree(start, new FileVisitor<>() {
    @Override
    public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
        System.out.println("preVisitDirectory : " + dir);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
        System.out.println("visitFile : " + file);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFileFailed(Path file, IOException exc) {
        System.out.println("visitFileFailed : " + file);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
        System.out.println("postVisitDirectory : " + dir);
        return FileVisitResult.CONTINUE;
    }
});

System.out.println("ret : " + ret);

// Result
// ↓
//-- start --
//preVisitDirectory : D:\java-work
//visitFileFailed : D:\java-work\dir1
//preVisitDirectory : D:\java-work\dir2
//visitFile : D:\java-work\dir2\aaa.txt
//postVisitDirectory : D:\java-work\dir2
//postVisitDirectory : D:\java-work
//ret : D:\java-work

static Path walkFileTree (Path start, Set<FileVisitOption> options, int maxDepth, FileVisitor<? super Path> visitor)

遍历文件树。 (机器翻译)

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//│  aaa.txt
//│  bbb.txt
//│
//├─dir1
//│  │  ccc.txt
//│  │  ddd.txt
//│  │
//│  └─dir1-2
//│          eee.txt
//│          fff.txt
//│
//└─dir2
//        ggg.txt
//        hhh.txt

final var start = Path.of("D:", "java-work");
System.out.println(start); // D:\java-work

final var visitor = new FileVisitor<Path>() {
    @Override
    public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
        System.out.println("preVisitDirectory : " + dir);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
        System.out.println("visitFile : " + file);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFileFailed(Path file, IOException exc) {
        System.out.println("visitFileFailed : " + file);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
        System.out.println("postVisitDirectory : " + dir);
        return FileVisitResult.CONTINUE;
    }
};

System.out.println("maxDepth : 3");
final var ret1 = Files.walkFileTree(start, Collections.emptySet(), 3, visitor);
System.out.println("ret : " + ret1);

// Result
// ↓
//maxDepth : 3
//preVisitDirectory : D:\java-work
//visitFile : D:\java-work\aaa.txt
//visitFile : D:\java-work\bbb.txt
//preVisitDirectory : D:\java-work\dir1
//visitFile : D:\java-work\dir1\ccc.txt
//visitFile : D:\java-work\dir1\ddd.txt
//preVisitDirectory : D:\java-work\dir1\dir1-2
//visitFile : D:\java-work\dir1\dir1-2\eee.txt
//visitFile : D:\java-work\dir1\dir1-2\fff.txt
//postVisitDirectory : D:\java-work\dir1\dir1-2
//postVisitDirectory : D:\java-work\dir1
//preVisitDirectory : D:\java-work\dir2
//visitFile : D:\java-work\dir2\ggg.txt
//visitFile : D:\java-work\dir2\hhh.txt
//postVisitDirectory : D:\java-work\dir2
//postVisitDirectory : D:\java-work
//ret : D:\java-work

System.out.println("maxDepth : 2");
final var ret2 = Files.walkFileTree(start, Collections.emptySet(), 2, visitor);
System.out.println("ret : " + ret2);

// Result
// ↓
//maxDepth : 2
//preVisitDirectory : D:\java-work
//visitFile : D:\java-work\aaa.txt
//visitFile : D:\java-work\bbb.txt
//preVisitDirectory : D:\java-work\dir1
//visitFile : D:\java-work\dir1\ccc.txt
//visitFile : D:\java-work\dir1\ddd.txt
//visitFile : D:\java-work\dir1\dir1-2
//postVisitDirectory : D:\java-work\dir1
//preVisitDirectory : D:\java-work\dir2
//visitFile : D:\java-work\dir2\ggg.txt
//visitFile : D:\java-work\dir2\hhh.txt
//postVisitDirectory : D:\java-work\dir2
//postVisitDirectory : D:\java-work
//ret : D:\java-work

System.out.println("maxDepth : 1");
final var ret3 = Files.walkFileTree(start, Collections.emptySet(), 1, visitor);
System.out.println("ret : " + ret3);

// Result
// ↓
//maxDepth : 1
//preVisitDirectory : D:\java-work
//visitFile : D:\java-work\aaa.txt
//visitFile : D:\java-work\bbb.txt
//visitFile : D:\java-work\dir1
//visitFile : D:\java-work\dir2
//postVisitDirectory : D:\java-work
//ret : D:\java-work

System.out.println("maxDepth : 0");
final var ret = Files.walkFileTree(start, Collections.emptySet(), 0, visitor);
System.out.println("ret : " + ret);

// Result
// ↓
//maxDepth : 0
//visitFile : D:\java-work
//ret : D:\java-work

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//├─dir
//│      aaa.txt
//│      bbb.txt
//│
//└─link-dir
//        aaa.txt
//        bbb.txt
//
//PS D:\java-work> ls
//
//    Directory: D:\java-work
//
//Mode   ...   Length Name
//----   ...   ------ ----
//d----  ...          dir
//l----  ...          link-dir -> D:\java-work\dir

final var start = Path.of("D:", "java-work");
System.out.println(start); // D:\java-work

final var visitor = new FileVisitor<Path>() {
    @Override
    public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
        System.out.println("preVisitDirectory : " + dir);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
        System.out.println("visitFile : " + file);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFileFailed(Path file, IOException exc) {
        System.out.println("visitFileFailed : " + file);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
        System.out.println("postVisitDirectory : " + dir);
        return FileVisitResult.CONTINUE;
    }
};

final var ret1 = Files.walkFileTree(
        start, Collections.emptySet(), Integer.MAX_VALUE, visitor);
System.out.println("ret : " + ret1);

// Result
// ↓
//preVisitDirectory : D:\java-work
//preVisitDirectory : D:\java-work\dir
//visitFile : D:\java-work\dir\aaa.txt
//visitFile : D:\java-work\dir\bbb.txt
//postVisitDirectory : D:\java-work\dir
//visitFile : D:\java-work\link-dir
//postVisitDirectory : D:\java-work
//ret : D:\java-work

System.out.println("FileVisitOption : FOLLOW_LINKS");
final var ret2 = Files.walkFileTree(
        start, Set.of(FileVisitOption.FOLLOW_LINKS), Integer.MAX_VALUE, visitor);
System.out.println("ret : " + ret2);

// Result
// ↓
//FileVisitOption : FOLLOW_LINKS
//preVisitDirectory : D:\java-work
//preVisitDirectory : D:\java-work\dir
//visitFile : D:\java-work\dir\aaa.txt
//visitFile : D:\java-work\dir\bbb.txt
//postVisitDirectory : D:\java-work\dir
//preVisitDirectory : D:\java-work\link-dir
//visitFile : D:\java-work\link-dir\aaa.txt
//visitFile : D:\java-work\link-dir\bbb.txt
//postVisitDirectory : D:\java-work\link-dir
//postVisitDirectory : D:\java-work
//ret : D:\java-work

// --- PowerShell ---
//PS D:\java-work> tree /F
//...
//D:.
//└─dir
//    │  aaa.txt
//    │  bbb.txt
//    │
//    └─link-parent-dir
//        │  aaa.txt
//        │  bbb.txt
//        │
//        └─link-parent-dir
//            │  aaa.txt
//            │  bbb.txt
// ...

// --- PowerShell ---
//PS D:\java-work> ls -Recurse
//
//    Directory: D:\java-work
//
//Mode   ...   Length Name
//----   ...   ----- ----
//d----  ...         dir
//
//    Directory: D:\java-work\dir
//
//Mode   ...   Length Name
//----   ...   ------ ----
//l----  ...          link-parent-dir -> D:\java-work\dir
//-a---  ...        0 aaa.txt
//-a---  ...        0 bbb.txt

// Symbolic links are circular.

final var start = Path.of("D:", "java-work");
System.out.println(start);

final var visitor = new FileVisitor<Path>() {
    @Override
    public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
        System.out.println("preVisitDirectory : " + dir);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
        System.out.println("visitFile : " + file);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult visitFileFailed(Path file, IOException exc) {
        System.out.println("visitFileFailed : " + file);
        return FileVisitResult.CONTINUE;
    }

    @Override
    public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
        System.out.println("postVisitDirectory : " + dir);
        return FileVisitResult.CONTINUE;
    }
};

final var ret = Files.walkFileTree(start,
        Set.of(FileVisitOption.FOLLOW_LINKS), Integer.MAX_VALUE, visitor);
System.out.println("ret : " + ret);

// Result
// ↓
//preVisitDirectory : D:\java-work
//preVisitDirectory : D:\java-work\dir
//visitFile : D:\java-work\dir\aaa.txt
//visitFile : D:\java-work\dir\bbb.txt
//visitFileFailed : D:\java-work\dir\link-parent-dir
//postVisitDirectory : D:\java-work\dir
//postVisitDirectory : D:\java-work
//ret : D:\java-work

static Path write (Path path, byte[] bytes, OpenOption... options)

将字节写入文件。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.data");
System.out.println(path); // D:\java-work\aaa.data
System.out.println(Files.notExists(path)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

final byte[] bytes1 = {0, 1, 2};
System.out.println(Files.write(path, bytes1)); // D:\java-work\aaa.data
System.out.println(Arrays.toString(Files.readAllBytes(path))); // [0, 1, 2]

final byte[] bytes2 = {3, 4, 5};
System.out.println(Files.write(path, bytes2)); // D:\java-work\aaa.data
System.out.println(Arrays.toString(Files.readAllBytes(path))); // [3, 4, 5]

final byte[] bytes3 = {6, 7, 8};
System.out.println(Files.write(
        path, bytes3, StandardOpenOption.APPEND)); // D:\java-work\aaa.data
System.out.println(Arrays.toString(Files.readAllBytes(path))); // [3, 4, 5, 6, 7, 8]

static Path write (Path path, Iterable<? extends CharSequence> lines, Charset cs, OpenOption... options)

将文本行写入文件。 (机器翻译)

final var sjis = Path.of("D:", "java-work", "aaa.txt");
System.out.println(sjis); // D:\java-work\aaa.txt
System.out.println(Files.notExists(sjis)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

final var ret1 = Files.write(sjis, List.of("〇", "△", "□"), Charset.forName("Shift_JIS"));
System.out.println(ret1); // D:\java-work\aaa.txt
System.out.println(Files.readAllLines(sjis, Charset.forName("Shift_JIS"))); // [〇, △, □]

try {
    Files.readAllLines(sjis, StandardCharsets.UTF_8);
} catch (MalformedInputException e) {
    System.out.println("MalformedInputException!");
}

// Result
// ↓
//MalformedInputException!

static Path write (Path path, Iterable<? extends CharSequence> lines, OpenOption... options)

将文本行写入文件。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt
System.out.println(Files.notExists(path)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

final var ret1 = Files.write(path, List.of("aaa", "bbb", "ccc"));
System.out.println(ret1); // D:\java-work\aaa.txt
System.out.println(Files.readAllLines(path)); // [aaa, bbb, ccc]

final var ret2 = Files.write(path, List.of("ddd", "eee", "fff"));
System.out.println(ret2); // D:\java-work\aaa.txt
System.out.println(Files.readAllLines(path)); // [ddd, eee, fff]

final var ret3 = Files.write(path,
        List.of("XXX", "YYY", "ZZZ"), StandardOpenOption.APPEND);
System.out.println(ret3); // D:\java-work\aaa.txt
System.out.println(Files.readAllLines(path)); // // [ddd, eee, fff, XXX, YYY, ZZZ]

static Path writeString (Path path, CharSequence csq, Charset cs, OpenOption... options)

将 CharSequence 写入文件。 (机器翻译)

final var sjis = Path.of("D:", "java-work", "aaa.txt");
System.out.println(sjis); // D:\java-work\aaa.txt
System.out.println(Files.notExists(sjis)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

final var ret = Files.writeString(sjis, "〇△□×", Charset.forName("Shift_JIS"));
System.out.println(ret); // D:\java-work\aaa.txt
System.out.println(Files.readString(sjis, Charset.forName("Shift_JIS"))); // 〇△□×

try {
    Files.readString(sjis, StandardCharsets.UTF_8);
} catch (MalformedInputException e) {
    System.out.println("MalformedInputException!");
}

// Result
// ↓
//MalformedInputException!

static Path writeString (Path path, CharSequence csq, OpenOption... options)

将 CharSequence 写入文件。 (机器翻译)

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt
System.out.println(Files.notExists(path)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

final var ret1 = Files.writeString(path, "abc");
System.out.println(ret1); // D:\java-work\aaa.txt
System.out.println(Files.readString(path)); // abc

final var ret2 = Files.writeString(path, "def");
System.out.println(ret2); // D:\java-work\aaa.txt
System.out.println(Files.readString(path)); // def

final var ret3 = Files.writeString(path, "XYZ", StandardOpenOption.APPEND);
System.out.println(ret3); // D:\java-work\aaa.txt
System.out.println(Files.readString(path)); // defXYZ

final var path = Path.of("D:", "java-work", "aaa.txt");
System.out.println(path); // D:\java-work\aaa.txt
System.out.println(Files.notExists(path)); // true

// --- PowerShell ---
//PS D:\java-work> ls
//<No files / directories>

final var csq = """
        abcd
        XYZ
        12345
        """;

final var ret = Files.writeString(path, csq);
System.out.println(ret); // D:\java-work\aaa.txt
System.out.println(Files.readAllLines(path)); // [abcd, XYZ, 12345]

API 示例

Java : Files 示例

简介

Methods

static long copy (InputStream in, Path target, CopyOption... options)

static long copy (Path source, OutputStream out)

static Path copy (Path source, Path target, CopyOption... options)

static Path createDirectories (Path dir, FileAttribute<?>... attrs)

static Path createDirectory (Path dir, FileAttribute<?>... attrs)

static Path createFile (Path path, FileAttribute<?>... attrs)

static Path createLink (Path link, Path existing)

static Path createSymbolicLink (Path link, Path target, FileAttribute<?>... attrs)

static Path createTempDirectory (String prefix, FileAttribute<?>... attrs)

static Path createTempDirectory (Path dir, String prefix, FileAttribute<?>... attrs)

static Path createTempFile (String prefix, String suffix, FileAttribute<?>... attrs)

static Path createTempFile (Path dir, String prefix, String suffix, FileAttribute<?>... attrs)

static void delete (Path path)

static boolean deleteIfExists (Path path)

static boolean exists (Path path, LinkOption... options)

static Stream<Path> find (Path start, int maxDepth, BiPredicate<Path,BasicFileAttributes> matcher, FileVisitOption... options)

static Object getAttribute (Path path, String attribute, LinkOption... options)

static <V extends FileAttributeView> V getFileAttributeView (Path path, Class<V> type, LinkOption... options)

static FileStore getFileStore (Path path)

static FileTime getLastModifiedTime (Path path, LinkOption... options)

static UserPrincipal getOwner (Path path, LinkOption... options)

static Set<PosixFilePermission> getPosixFilePermissions (Path path, LinkOption... options)

static boolean isDirectory (Path path, LinkOption... options)

static boolean isExecutable (Path path)

static boolean isHidden (Path path)

static boolean isReadable (Path path)

static boolean isRegularFile (Path path, LinkOption... options)

static boolean isSameFile (Path path, Path path2)

static boolean isSymbolicLink (Path path)

static boolean isWritable (Path path)

static Stream<String> lines (Path path)

static Stream<String> lines (Path path, Charset cs)

static Stream<Path> list (Path dir)

static long mismatch (Path path, Path path2)

static Path move (Path source, Path target, CopyOption... options)

static BufferedReader newBufferedReader (Path path)

static BufferedReader newBufferedReader (Path path, Charset cs)

static BufferedWriter newBufferedWriter (Path path, Charset cs, OpenOption... options)

static BufferedWriter newBufferedWriter (Path path, OpenOption... options)

static SeekableByteChannel newByteChannel (Path path, OpenOption... options)

static SeekableByteChannel newByteChannel (Path path, Set<? extends OpenOption> options, FileAttribute<?>... attrs)

static DirectoryStream<Path> newDirectoryStream (Path dir)

static DirectoryStream<Path> newDirectoryStream (Path dir, String glob)

static DirectoryStream<Path> newDirectoryStream (Path dir, DirectoryStream.Filter<? super Path> filter)

static InputStream newInputStream (Path path, OpenOption... options)

static OutputStream newOutputStream (Path path, OpenOption... options)

static boolean notExists (Path path, LinkOption... options)

static String probeContentType (Path path)

static byte[] readAllBytes (Path path)

static List<String> readAllLines (Path path)

static List<String> readAllLines (Path path, Charset cs)

static <A extends BasicFileAttributes> A readAttributes (Path path, Class<A> type, LinkOption... options)

static Map<String,Object> readAttributes (Path path, String attributes, LinkOption... options)

static String readString (Path path)

static String readString (Path path, Charset cs)

static Path readSymbolicLink (Path link)

static Path setAttribute (Path path, String attribute, Object value, LinkOption... options)

static Path setLastModifiedTime (Path path, FileTime time)

static Path setOwner (Path path, UserPrincipal owner)

static Path setPosixFilePermissions (Path path, Set<PosixFilePermission> perms)

static long size (Path path)

static Stream<Path> walk (Path start, int maxDepth, FileVisitOption... options)

static Stream<Path> walk (Path start, FileVisitOption... options)

static Path walkFileTree (Path start, FileVisitor<? super Path> visitor)

static Path walkFileTree (Path start, Set<FileVisitOption> options, int maxDepth, FileVisitor<? super Path> visitor)

static Path write (Path path, byte[] bytes, OpenOption... options)

static Path write (Path path, Iterable<? extends CharSequence> lines, Charset cs, OpenOption... options)

static Path write (Path path, Iterable<? extends CharSequence> lines, OpenOption... options)

static Path writeString (Path path, CharSequence csq, Charset cs, OpenOption... options)

static Path writeString (Path path, CharSequence csq, OpenOption... options)

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