Files (Java SE 22 & JDK 22) の使い方まとめです。
ほとんどのメソッドにサンプルコードがあります。
API仕様書のおともにどうぞ。
概要
このクラスは、ファイル、ディレクトリ、またはその他の種類のファイルを操作するstaticメソッドだけで構成されます。
Filesクラスには、
- ファイルの読み書き、コピー、削除
- ディレクトリの作成、削除
などなど、実際のファイルやディレクトリへアクセスするためのメソッドが数多くそろっています。
具体的なアクセス対象を指定するには Pathインタフェースを使います。
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
//<ファイル・ディレクトリなし>
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
//<ファイル・ディレクトリなし>
関連記事 : ファイル操作の基本
注意
- 基本は Windows 10 で実行した結果となります。
- 一部 POSIX 環境でないと確認できないものは、Linux で実行しています。
メソッド
static long copy (InputStream in, Path target, CopyOption... options)
すべてのバイトを入力ストリームからファイルにコピーします。
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
//<ファイル・ディレクトリなし>
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);
// 結果
// ↓
//<!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!");
}
// 結果
// ↓
//FileAlreadyExistsException!
try (final var in = new ByteArrayInputStream(buf)) {
Files.copy(in, target, StandardCopyOption.REPLACE_EXISTING);
System.out.println(Arrays.toString(Files.readAllBytes(target)));
}
// 結果
// ↓
//[10, 20, 30]
static long copy (Path source, OutputStream out)
すべてのバイトをファイルから出力ストリームにコピーします。
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
//<ファイル・ディレクトリなし>
try (final var out = new ByteArrayOutputStream()) {
Files.copy(source, out);
} catch (NoSuchFileException e) {
System.out.println("NoSuchFileException!");
}
// 結果
// ↓
//NoSuchFileException!
static Path copy (Path source, Path target, CopyOption... options)
ファイルをターゲット・ファイルにコピーします。
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!");
}
// 結果
// ↓
//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
//<ファイル・ディレクトリなし>
try {
Files.copy(source, target);
} catch (NoSuchFileException e) {
System.out.println("NoSuchFileException!");
}
// 結果
// ↓
//NoSuchFileException!
static Path createDirectories (Path dir, FileAttribute<?>... attrs)
存在しないすべての親ディレクトリをまず作成することで、ディレクトリを作成します。
FileAttribute については、createFile(Path path, FileAttribute<?>... attrs) の使用例をご参照ください。
// --- 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!");
}
// 結果
// ↓
//FileAlreadyExistsException!
static Path createDirectory (Path dir, FileAttribute<?>... attrs)
新しいディレクトリを作成します。
FileAttribute については、createFile(Path path, FileAttribute<?>... attrs) の使用例をご参照ください。
// --- 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!");
}
// 結果
// ↓
//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!");
}
// 結果
// ↓
//NoSuchFileException!
static Path createFile (Path path, FileAttribute<?>... attrs)
新しい空のファイルを作成し、ファイルがすでに存在する場合は失敗します。
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
//<ファイル・ディレクトリなし>
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!");
}
// 結果
// ↓
//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
//<ファイル・ディレクトリなし>
try {
Files.createFile(path);
} catch (NoSuchFileException e) {
System.out.println("NoSuchFileException!");
}
// 結果
// ↓
//NoSuchFileException!
以下のコード例は Linux 上で実行しています。
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)
既存のファイルに対して新しいリンク(ディレクトリ・エントリ)を作成します(オプションの操作)。
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
//<ファイル・ディレクトリなし>
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!");
}
// 結果
// ↓
//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!");
}
// 結果
// ↓
//FileAlreadyExistsException!
static Path createSymbolicLink (Path link, Path target, FileAttribute<?>... attrs)
ターゲットへのシンボリック・リンクを作成します(オプションの操作)。
シンボリック・リンクの作成には管理者権限を必要とする場合があります。
FileAttribute については、createFile(Path path, FileAttribute<?>... attrs) の使用例をご参照ください。
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
//<ファイル・ディレクトリなし>
// 実体のないリンクも作成可能です。
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!");
}
// 結果
// ↓
//FileAlreadyExistsException!
static Path createTempDirectory (String prefix, FileAttribute<?>... attrs)
デフォルトの一時ファイル・ディレクトリで新しいディレクトリを生成し、その名前には、指定された接頭辞が使用されます。
FileAttribute については、createFile(Path path, FileAttribute<?>... attrs) の使用例をご参照ください。
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)
指定されたディレクトリで新しいディレクトリを生成し、その名前には、指定された接頭辞が使用されます。
FileAttribute については、createFile(Path path, FileAttribute<?>... attrs) の使用例をご参照ください。
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)
指定された接頭辞と接尾辞をファイル名の生成に使用して、デフォルトの一時ファイル・ディレクトリに空のファイルを生成します。
FileAttribute については、createFile(Path path, FileAttribute<?>... attrs) の使用例をご参照ください。
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)
指定されたディレクトリで新しい空のファイルを生成し、その名前には、指定された接頭辞および接尾辞の文字列が使用されます。
FileAttribute については、createFile(Path path, FileAttribute<?>... attrs) の使用例をご参照ください。
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)
ファイルを削除します。
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
//<ファイル・ディレクトリなし>
// --- PowerShell ---
//PS D:\java-work> ls
//<ファイル・ディレクトリなし>
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!");
}
// 結果
// ↓
//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!");
}
// 結果
// ↓
//DirectoryNotEmptyException!
static boolean deleteIfExists (Path path)
ファイルが存在する場合は削除します。
delete(Path path) の使用例もご参照ください。
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
//<ファイル・ディレクトリなし>
System.out.println(Files.deleteIfExists(path)); // false
static boolean exists (Path path, LinkOption... options)
ファイルが存在するかどうかをテストします。
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
// 意図的にリンク先のファイルが存在しない状態にします。
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)
指定された開始ファイルをルートとするファイル・ツリー内でファイルを検索することで Pathが遅延設定されるStreamを返します。
// --- 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);
}
// 結果
// ↓
//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);
}
// 結果
// ↓
//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);
}
// 結果
// ↓
//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);
}
// 結果
// ↓
//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);
}
// 結果
// ↓
//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);
}
// 結果
// ↓
//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);
}
// 結果
// ↓
//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);
}
// 結果
// ↓
//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!");
}
// 結果
// ↓
//NoSuchFileException!
static Object getAttribute (Path path, String attribute, LinkOption... options)
ファイル属性の値を読み取ります。
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)
指定されたタイプのファイル属性ビューを返します。
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)
ファイルが置かれているファイル・ストアを表すFileStoreを返します。
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)
ファイルの最終変更時間を返します。
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はUTCです。
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)
ファイルの所有者を返します。
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)
ファイルのPOSIXファイル・アクセス権を返します。
以下のコード例は Linux 上で実行しています。
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)
ファイルがディレクトリかどうかをテストします。
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)
ファイルが実行可能かどうかをテストします。
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
// Windowsの場合、実行ファイル以外も基本的に実行権がついています。
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
以下のコード例は Linux 上で実行しています。
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)
ファイルが隠しファイルとみなされるかどうかを判断します。
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!");
}
// 結果
// ↓
//NoSuchFileException!
static boolean isReadable (Path path)
ファイルが読取り可能かどうかをテストします。
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
// ※non-readable.txtは読み取り権限を拒否にしています。
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)
ファイルが不透明な内容の通常ファイルかどうかをテストします。
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)
2つのパスが同じファイルを検出するかどうかを判断します。
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!");
}
// 結果
// ↓
//NoSuchFileException!
static boolean isSymbolicLink (Path path)
ファイルがシンボリック・リンクかどうかをテストします。
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)
ファイルが書込み可能かどうかをテストします。
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)
ファイル内のすべての行をStreamとして読み取ります。
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)
ファイル内のすべての行をStreamとして読み取ります。
パラメータ cs 以外については、lines(Path path) の使用例もご参照ください。
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());
}
// 結果
// ↓
//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());
}
// 結果
// ↓
//UncheckedIOException! : java.nio.charset.MalformedInputException: Input length = 1
static Stream<Path> list (Path dir)
ディレクトリ内のエントリを要素に持つ遅延設定Streamを返します。
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);
// 結果
// ↓
//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);
// 結果
// ↓
//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!");
}
// 結果
// ↓
//NotDirectoryException!
static long mismatch (Path path, Path path2)
2つのファイルのコンテンツ内で、最初の不一致バイトの位置を検索して返します。不一致がない場合は、-1L。
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)
ファイルをターゲット・ファイルに移動するか、そのファイル名を変更します。
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!");
}
// 結果
// ↓
//FileAlreadyExistsException!
// 異なるFileStoreへファイルを移動する例です。
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
// 異なるFileStoreへディレクトリを移動する例です。
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!");
}
// 結果
// ↓
//DirectoryNotEmptyException!
static BufferedReader newBufferedReader (Path path)
ファイルを読込み用に開き、効率的な方法でファイルからテキストを読み込むBufferedReaderを返します。
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)
ファイルを読取り用に開き、そのファイルから効果的な方法でテキストを読み取るために使用できるBufferedReaderを返します。
パラメータ cs 以外については、newBufferedReader(Path path) の使用例もご参照ください。
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!");
}
// 結果
// ↓
//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!");
}
// 結果
// ↓
//MalformedInputException!
static BufferedWriter newBufferedWriter (Path path, Charset cs, OpenOption... options)
ファイルを書込み用に開くか作成して、そのファイルに効果的な方法でテキストを書き込むために使用できるBufferedWriterを返します。
パラメータ cs 以外については、newBufferedWriter(Path path, OpenOption... options) の使用例もご参照ください。
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!");
}
// 結果
// ↓
//MalformedInputException!
static BufferedWriter newBufferedWriter (Path path, OpenOption... options)
ファイルを書込み用に開くか作成し、効率的な方法でファイルにテキストを書き込むBufferedWriterを返します。
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);
// 結果
// ↓
//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)
ファイルを開くか作成し、そのファイルにアクセスするためのシーク可能なバイト・チャネルを返します。
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
//<ファイル・ディレクトリなし>
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)
ファイルを開くか作成し、そのファイルにアクセスするためのシーク可能なバイト・チャネルを返します。
FileAttribute については、createFile(Path path, FileAttribute<?>... attrs) の使用例をご参照ください。
それ以外については newByteChannel(Path path, OpenOption... options) をご参照ください。
static DirectoryStream<Path> newDirectoryStream (Path dir)
ディレクトリを開き、ディレクトリ内のすべてのエントリを反復するためのDirectoryStreamを返します。
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);
}
}
// 結果
// ↓
//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);
}
}
// 結果
// ↓
//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!");
}
// 結果
// ↓
//NoSuchFileException!
static DirectoryStream<Path> newDirectoryStream (Path dir, String glob)
ディレクトリを開き、そのディレクトリ内のエントリに対して反復処理を行うDirectoryStreamを返します。
パラメータ glob 以外については、newDirectoryStream(Path dir) をご参照ください。
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);
}
}
// 結果
// ↓
//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);
}
}
// 結果
// ↓
//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);
}
}
// 結果
// ↓
//D:\java-work\bbb.txt
//D:\java-work\Book.java
static DirectoryStream<Path> newDirectoryStream (Path dir, DirectoryStream.Filter<? super Path> filter)
ディレクトリを開き、そのディレクトリ内のエントリに対して反復処理を行うDirectoryStreamを返します。
パラメータ filter 以外については、newDirectoryStream(Path dir) をご参照ください。
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);
}
}
// 結果
// ↓
//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);
}
}
// 結果
// ↓
//D:\java-work\Book.java
//D:\java-work\Page.java
static InputStream newInputStream (Path path, OpenOption... options)
ファイルを開き、そのファイルから読み取る入力ストリームを返します。
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);
}
// 結果
// ↓
//java.io.IOException: File is symbolic link
static OutputStream newOutputStream (Path path, OpenOption... options)
ファイルを開くか作成して、そのファイルにバイトを書き込むために使用できる出力ストリームを返します。
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)
このパスが示すファイルが存在しないかどうかをテストします。
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)
ファイルのコンテンツ・タイプを調べます。
// --- 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)
ファイルからすべてのバイトを読み取ります。
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)
ファイルからすべての行を読み取ります。
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)
ファイルからすべての行を読み取ります。
パラメータ cs 以外については、readAllLines(Path path) の使用例もご参照ください。
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!");
}
// 結果
// ↓
//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!");
}
// 結果
// ↓
//MalformedInputException!
static <A extends BasicFileAttributes> A readAttributes (Path path, Class<A> type, LinkOption... options)
一括操作としてファイル属性を読み取ります。
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)
一括操作として一連のファイル属性を読み取ります。
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)
ファイルのすべてのコンテンツを文字列に読み込み、UTF-8 charsetを使用してバイトから文字にデコードします。
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);
// 結果
// ↓
//abcd
//XYZ
//12345
static String readString (Path path, Charset cs)
ファイルのすべての文字を文字列に読み込み、指定されたcharsetを使用してバイトから文字にデコードします。
パラメータ cs 以外については、readString(Path path) の使用例もご参照ください。
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!");
}
// 結果
// ↓
//MalformedInputException!
static Path readSymbolicLink (Path link)
シンボリック・リンクのターゲットを読み取ります(オプションの操作)。
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!");
}
// 結果
// ↓
//NotLinkException!
static Path setAttribute (Path path, String attribute, Object value, LinkOption... options)
ファイル属性の値を設定します。
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)
ファイルの最終変更時間属性を更新します。
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はUTCです。
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)
ファイル所有者を更新します。
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)
ファイルのPOSIXファイル・アクセス権を設定します。
以下のコード例は Linux 上で実行しています。
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)
ファイルのサイズをバイトで返します。
// --- 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!");
}
// 結果
// ↓
//NoSuchFileException!
static Stream<Path> walk (Path start, int maxDepth, FileVisitOption... options)
指定された開始ファイルをルートとするファイル・ツリーを参照することで Pathが遅延移入されるStreamを返します。
パラメータ maxDepth 以外については、walk(Path start, FileVisitOption... options) の使用例もご参照ください。
// --- 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);
}
// 結果
// ↓
//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);
}
// 結果
// ↓
//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);
}
// 結果
// ↓
//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);
}
// 結果
// ↓
//maxDepth : 0
//D:\java-work
static Stream<Path> walk (Path start, FileVisitOption... options)
指定された開始ファイルをルートとするファイル・ツリーを参照することで Pathが遅延移入されるStreamを返します。
// --- 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);
}
// 結果
// ↓
//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);
}
// 結果
// ↓
//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);
}
// 結果
// ↓
//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
// ※link-parent-dirは親のdirへのシンボリックリンクです。
// つまりリンクが循環しています。
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);
}
// 結果
// ↓
//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);
}
// 結果
// ↓
//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!");
}
// 結果
// ↓
//NoSuchFileException!
static Path walkFileTree (Path start, FileVisitor<? super Path> visitor)
ファイル・ツリーを参照します。
// --- 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);
// 結果
// ↓
//-- 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);
// 結果
// ↓
//-- 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);
// 結果
// ↓
//-- 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…
// ※意図的に失敗ケースを発生させるために、dir1ディレクトリは読み取り権限を外しています。
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);
// 結果
// ↓
//-- 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)
ファイル・ツリーを参照します。
パラメータ options, maxDepth 以外については、walkFileTree(Path start, FileVisitor<? super Path> visitor) の使用例もご参照ください。
// --- 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);
// 結果
// ↓
//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);
// 結果
// ↓
//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);
// 結果
// ↓
//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);
// 結果
// ↓
//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);
// 結果
// ↓
//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);
// 結果
// ↓
//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
// ※link-parent-dirは親のdirへのシンボリックリンクです。
// つまりリンクが循環しています。
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);
// 結果
// ↓
//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)
バイトをファイルに書き込みます。
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
//<ファイル・ディレクトリなし>
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)
テキスト行をファイルに書き込みます。
パラメータ cs 以外については、write(Path path, Iterable<? extends CharSequence> lines, OpenOption... options) の使用例もご参照ください。
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
//<ファイル・ディレクトリなし>
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!");
}
// 結果
// ↓
//MalformedInputException!
static Path write (Path path, Iterable<? extends CharSequence> lines, OpenOption... options)
テキスト行をファイルに書き込みます。
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
//<ファイル・ディレクトリなし>
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)
CharSequenceをファイルに書き込みます。
パラメータ cs 以外については、writeString(Path path, CharSequence csq, OpenOption... options) の使用例もご参照ください。
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
//<ファイル・ディレクトリなし>
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!");
}
// 結果
// ↓
//MalformedInputException!
static Path writeString (Path path, CharSequence csq, OpenOption... options)
CharSequenceをファイルに書き込みます。
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
//<ファイル・ディレクトリなし>
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
//<ファイル・ディレクトリなし>
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]