Java : Formatter (String Syntax) 示例

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

注解 :

本文可能使用了翻译软件以方便阅读。另请查看英文原文。

简介

printf 样式格式字符串的解释器。此类支持布局对齐和对齐、数字、字符串和日期/时间数据的通用格式以及特定于语言环境的输出。 (机器翻译)

Class diagram

try (final var formatter = new Formatter()) {
    formatter.format("str = %s : num = %d", "abc", 1234);

    final var str = formatter.toString();
    System.out.println(str); // str = abc : num = 1234
}

try (final var formatter = new Formatter()) {
    final var value = "abc";
    formatter.format("%s : %S", value, value);

    final var str = formatter.toString();
    System.out.println(str); // abc : ABC
}

try (final var formatter = new Formatter()) {
    final var value = 'x';
    formatter.format("%c : %C", value, value);

    final var str = formatter.toString();
    System.out.println(str); // x : X
}

try (final var formatter = new Formatter()) {
    final var value = 255;
    formatter.format("%d : %x : %X", value, value, value);

    final var str = formatter.toString();
    System.out.println(str); // 255 : ff : FF
}

try (final var formatter = new Formatter()) {
    final var value = 0.12345;
    formatter.format("%e : %f", value, value);

    final var str = formatter.toString();
    System.out.println(str); // 1.234500e-01 : 0.123450
}

try (final var formatter = new Formatter()) {
    formatter.format("%1$d : %2$d : %3$d", 111, 222, 333);
    System.out.println(formatter); // 111 : 222 : 333
}

try (final var formatter = new Formatter()) {
    formatter.format("%3$d : %2$d : %1$d", 111, 222, 333);
    System.out.println(formatter); // 333 : 222 : 111
}

Constructors

Formatter ()

构造一个新的格式化程序。 (机器翻译)

try (final var formatter = new Formatter()) {
    formatter.format("%s : %d", "abc", 1234);
    System.out.println(formatter); // abc : 1234
}

Formatter (File file)

使用指定的文件构造一个新的格式化程序。 (机器翻译)

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

try (final var formatter = new Formatter(file.toFile())) {
    formatter.format("%s : %d", "abc", 1234);
}

System.out.println(Files.readString(file)); // abc : 1234

Formatter (File file, String csn)

使用指定的文件和字符集构造一个新的格式化程序。 (机器翻译)

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

final var csn = "Shift_JIS";

try (final var formatter = new Formatter(file.toFile(), csn)) {
    formatter.format("%s : %d", "○△×", 1234);
}

System.out.println(Files.readString(file, Charset.forName(csn))); // ○△× : 1234

Formatter (File file, String csn, Locale l)

使用指定的文件、字符集和语言环境构造一个新的格式化程序。 (机器翻译)

System.out.println(Locale.getDefault().toLanguageTag()); // en-US

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

final var csn = StandardCharsets.UTF_8.name();
System.out.println(csn); // UTF-8

try (final var formatter = new Formatter(file.toFile(), csn)) {
    formatter.format("%tA", DayOfWeek.SUNDAY);
}
System.out.println(Files.readString(file, Charset.forName(csn))); // Sunday

try (final var formatter = new Formatter(file.toFile(), csn, Locale.JAPAN)) {
    formatter.format("%tA", DayOfWeek.SUNDAY);
}
System.out.println(Files.readString(file, Charset.forName(csn))); // 日曜日

Formatter (File file, Charset charset, Locale l)

使用指定的文件、字符集和语言环境构造一个新的格式化程序。 (机器翻译)

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

final var charset = StandardCharsets.UTF_8;

try (final var formatter = new Formatter(file.toFile(), charset, Locale.US)) {
    formatter.format("%tA", DayOfWeek.SUNDAY);
}
System.out.println(Files.readString(file, charset)); // Sunday

try (final var formatter = new Formatter(file.toFile(), charset, Locale.JAPAN)) {
    formatter.format("%tA", DayOfWeek.SUNDAY);
}
System.out.println(Files.readString(file, charset)); // 日曜日

Formatter (OutputStream os)

用指定的输出流构造一个新的格式化程序。 (机器翻译)

final var os = new ByteArrayOutputStream();
try (final var formatter = new Formatter(os)) {
    formatter.format("%s : %d", "abc", 1234);
}

System.out.println(os); // abc : 1234

Formatter (OutputStream os, String csn)

使用指定的输出流和字符集构造一个新的格式化程序。 (机器翻译)

final var csn = "Shift_JIS";

final var os = new ByteArrayOutputStream();
try (final var formatter = new Formatter(os, csn)) {
    formatter.format("%s : %d", "○△×", 1234);
}

System.out.println(os.toString(csn)); // ○△× : 1234

Formatter (OutputStream os, String csn, Locale l)

使用指定的输出流、字符集和语言环境构造一个新的格式化程序。 (机器翻译)

System.out.println(Locale.getDefault().toLanguageTag()); // en-US

final var csn = StandardCharsets.UTF_8.name();
System.out.println(csn); // UTF-8

{
    final var os = new ByteArrayOutputStream();
    try (final var formatter = new Formatter(os, csn)) {
        formatter.format("%tA", DayOfWeek.SUNDAY);
    }
    System.out.println(os.toString(csn)); // Sunday
}
{
    final var os = new ByteArrayOutputStream();
    try (final var formatter = new Formatter(os, csn, Locale.JAPAN)) {
        formatter.format("%tA", DayOfWeek.SUNDAY);
    }
    System.out.println(os.toString(csn)); // 日曜日
}

Formatter (OutputStream os, Charset charset, Locale l)

使用指定的输出流、字符集和语言环境构造一个新的格式化程序。 (机器翻译)

final var charset = StandardCharsets.UTF_8;

final var os = new ByteArrayOutputStream();
try (final var formatter = new Formatter(os, charset, Locale.US)) {
    formatter.format("%tA", DayOfWeek.SUNDAY);
}
System.out.println(os.toString(charset)); // Sunday

final var charset = StandardCharsets.UTF_8;

final var os = new ByteArrayOutputStream();
try (final var formatter = new Formatter(os, charset, Locale.JAPAN)) {
    formatter.format("%tA", DayOfWeek.SUNDAY);
}
System.out.println(os.toString(charset)); // 日曜日

Formatter (PrintStream ps)

使用指定的打印流构造一个新的格式化程序。 (机器翻译)

final var out = new ByteArrayOutputStream();
try (final var ps = new PrintStream(out)) {

    try (final var formatter = new Formatter(ps)) {
        formatter.format("%s : %d", "abc", 1234);
    }
}

System.out.println(out); // abc : 1234

Formatter (Appendable a)

构造一个具有指定目标的新格式化程序。 (机器翻译)

final var a = new StringBuilder();
try (final var formatter = new Formatter(a)) {
    formatter.format("%s : %d", "abc", 1234);
}

System.out.println(a); // abc : 1234

Formatter (Appendable a, Locale l)

构造具有指定目标和语言环境的新格式化程序。 (机器翻译)

System.out.println(Locale.getDefault().toLanguageTag()); // en-US

{
    final var a = new StringBuilder();
    try (final var formatter = new Formatter(a)) {
        formatter.format("%tA", DayOfWeek.SUNDAY);
    }
    System.out.println(a); // Sunday
}
{
    final var a = new StringBuilder();
    try (final var formatter = new Formatter(a, Locale.JAPAN)) {
        formatter.format("%tA", DayOfWeek.SUNDAY);
    }
    System.out.println(a); // 日曜日
}

Formatter (String fileName)

用指定的文件名构造一个新的格式化程序。 (机器翻译)

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

try (final var formatter = new Formatter(fileName)) {
    formatter.format("%s : %d", "abc", 1234);
}

System.out.println(Files.readString(file)); // abc : 1234

Formatter (String fileName, String csn)

用指定的文件名和字符集构造一个新的格式化程序。 (机器翻译)

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

final var csn = "Shift_JIS";

try (final var formatter = new Formatter(fileName, csn)) {
    formatter.format("%s : %d", "○△×", 1234);
}

System.out.println(Files.readString(file, Charset.forName(csn))); // ○△× : 1234

Formatter (String fileName, String csn, Locale l)

使用指定的文件名、字符集和语言环境构造一个新的格式化程序。 (机器翻译)

System.out.println(Locale.getDefault().toLanguageTag()); // en-US

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

final var csn = StandardCharsets.UTF_8.name();
System.out.println(csn); // UTF-8

try (final var formatter = new Formatter(fileName, csn)) {
    formatter.format("%tA", DayOfWeek.SUNDAY);
}
System.out.println(Files.readString(file, Charset.forName(csn))); // Sunday

try (final var formatter = new Formatter(fileName, csn, Locale.JAPAN)) {
    formatter.format("%tA", DayOfWeek.SUNDAY);
}
System.out.println(Files.readString(file, Charset.forName(csn))); // 日曜日

Formatter (String fileName, Charset charset, Locale l)

使用指定的文件名、字符集和语言环境构造一个新的格式化程序。 (机器翻译)

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

final var charset = StandardCharsets.UTF_8;

try (final var formatter = new Formatter(fileName, charset, Locale.US)) {
    formatter.format("%tA", DayOfWeek.SUNDAY);
}
System.out.println(Files.readString(file, charset)); // Sunday

try (final var formatter = new Formatter(fileName, charset, Locale.JAPAN)) {
    formatter.format("%tA", DayOfWeek.SUNDAY);
}
System.out.println(Files.readString(file, charset)); // 日曜日

Formatter (Locale l)

构造具有指定语言环境的新格式化程序。 (机器翻译)

try (final var formatter = new Formatter(Locale.US)) {
    formatter.format("%tA", DayOfWeek.SUNDAY);
    System.out.println(formatter); // Sunday
}

try (final var formatter = new Formatter(Locale.JAPAN)) {
    formatter.format("%tA", DayOfWeek.SUNDAY);
    System.out.println(formatter); // 日曜日
}

Methods

void close ()

关闭此格式化程序。 (机器翻译)

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

try (final var formatter = new Formatter(file.toFile())) {
    formatter.format("%s : %d", "abc", 1234);
}

System.out.println(Files.readString(file)); // abc : 1234

// An example without a try-with-resources statement.
final var file = Path.of("R:", "java-work", "aaa.txt");
System.out.println(file); // R:\java-work\aaa.txt

final var formatter = new Formatter(file.toFile());
try {
    formatter.format("%s : %d", "abc", 1234);
} finally {
    formatter.close();
}

System.out.println(Files.readString(file)); // abc : 1234

void flush ()

刷新此格式化程序。 (机器翻译)

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

try (final var formatter = new Formatter(file.toFile())) {

    formatter.format("abc");
    System.out.println(Files.readString(file).isEmpty()); // true

    formatter.flush();
    System.out.println(Files.readString(file)); // abc

    formatter.format("XYZ");
    System.out.println(Files.readString(file)); // abc
}

System.out.println(Files.readString(file)); // abcXYZ

Formatter format (String format, Object... args)

使用指定的格式字符串和参数将格式化的字符串写入此对象的目标。 (机器翻译)

try (final var formatter = new Formatter()) {
    final var value = "abc";
    formatter.format("%s : %S", value, value);

    final var str = formatter.toString();
    System.out.println(str); // abc : ABC
}

try (final var formatter = new Formatter()) {
    final var value = 'x';
    formatter.format("%c : %C", value, value);

    final var str = formatter.toString();
    System.out.println(str); // x : X
}

try (final var formatter = new Formatter()) {
    final var value = 255;
    formatter.format("%d : %x : %X", value, value, value);

    final var str = formatter.toString();
    System.out.println(str); // 255 : ff : FF
}

try (final var formatter = new Formatter()) {
    final var value = 0.12345;
    formatter.format("%e : %f", value, value);

    final var str = formatter.toString();
    System.out.println(str); // 1.234500e-01 : 0.123450
}

Formatter format (Locale l, String format, Object... args)

使用指定的语言环境、格式字符串和参数将格式化的字符串写入此对象的目标。 (机器翻译)

System.out.println(Locale.getDefault().toLanguageTag()); // en-US

try (final var formatter = new Formatter()) {
    formatter.format("%tA", DayOfWeek.SUNDAY);
    System.out.println(formatter); // Sunday
}

try (final var formatter = new Formatter()) {
    formatter.format(Locale.JAPAN, "%tA", DayOfWeek.SUNDAY);
    System.out.println(formatter); // 日曜日
}

IOException ioException ()

返回此格式化程序的 Appendable 最后抛出的 IOException。 (机器翻译)

try (final var formatter = new Formatter()) {

    formatter.format("%s : %d", "abc", 1234);
    System.out.println(formatter); // abc : 1234

    final var ret = formatter.ioException();
    System.out.println(ret); // null
}

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

try (final var out = Files.newOutputStream(file);
     final var formatter = new Formatter(out)) {

    // Intentionally closes the out object to make an error.
    out.close();

    formatter.format("%s : %d", "abc", 1234);
    formatter.flush();

    final var ret = formatter.ioException();
    System.out.println(ret); // java.nio.channels.ClosedChannelException
}

Locale locale ()

返回此格式化程序构造所设置的语言环境。 (机器翻译)

System.out.println(Locale.getDefault().toLanguageTag()); // en-US

try (final var formatter = new Formatter()) {
    System.out.println(formatter.locale().toLanguageTag()); // en-US

    formatter.format("%tA", DayOfWeek.SUNDAY);
    System.out.println(formatter); // Sunday
}

try (final var formatter = new Formatter(Locale.JAPAN)) {
    System.out.println(formatter.locale().toLanguageTag()); // ja-JP

    formatter.format("%tA", DayOfWeek.SUNDAY);
    System.out.println(formatter); // 日曜日
}

Appendable out ()

返回输出的目的地。 (机器翻译)

try (final var formatter = new Formatter()) {
    final var out = formatter.out();
    System.out.println(out.getClass().getSimpleName()); // StringBuilder
}

try (final var formatter = new Formatter(new ByteArrayOutputStream())) {
    final var out = formatter.out();
    System.out.println(out.getClass().getSimpleName()); // BufferedWriter
}

String toString ()

返回在输出目标上调用 toString() 的结果。 (机器翻译)

try (final var formatter = new Formatter()) {
    final var value = "abc";
    formatter.format("%s : %S", value, value);

    final var str = formatter.toString();
    System.out.println(str); // abc : ABC
}

try (final var formatter = new Formatter()) {
    final var value = 'x';
    formatter.format("%c : %C", value, value);

    final var str = formatter.toString();
    System.out.println(str); // x : X
}

try (final var formatter = new Formatter()) {
    final var value = 255;
    formatter.format("%d : %x : %X", value, value, value);

    final var str = formatter.toString();
    System.out.println(str); // 255 : ff : FF
}

try (final var formatter = new Formatter()) {
    final var value = 0.12345;
    formatter.format("%e : %f", value, value);

    final var str = formatter.toString();
    System.out.println(str); // 1.234500e-01 : 0.123450
}

API 示例

Java : Formatter (String Syntax) 示例

简介

Constructors

Formatter ()

Formatter (File file)

Formatter (File file, String csn)

Formatter (File file, String csn, Locale l)

Formatter (File file, Charset charset, Locale l)

Formatter (OutputStream os)

Formatter (OutputStream os, String csn)

Formatter (OutputStream os, String csn, Locale l)

Formatter (OutputStream os, Charset charset, Locale l)

Formatter (PrintStream ps)

Formatter (Appendable a)

Formatter (Appendable a, Locale l)

Formatter (String fileName)

Formatter (String fileName, String csn)

Formatter (String fileName, String csn, Locale l)

Formatter (String fileName, Charset charset, Locale l)

Formatter (Locale l)

Methods

void close ()

void flush ()

Formatter format (String format, Object... args)

Formatter format (Locale l, String format, Object... args)

IOException ioException ()

Locale locale ()

Appendable out ()

String toString ()

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