2025年4月8日
Java 中的 AutoCloseable (Java SE 23 & JDK 23) 及其示例。
您将找到大多数 AutoCloseable 方法的代码示例。
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
可以保存资源（如文件或套接字句柄）直到关闭的对象。退出 try-with-resources 块时，将自动调用 AutoCloseable 对象的 close() 方法，该块已在资源规范标头中声明了该对象。 (机器翻译)
class Sample implements AutoCloseable {
@Override
public void close() {
System.out.println("close : called!");
}
public void print() {
System.out.println("print!");
}
}
// The close() method of an AutoCloseable object is called automatically
// when exiting a try-with-resources block.
try (final var sample = new Sample()) {
sample.print();
}
System.out.println("end!");
// Result
// ↓
//print!
//close : called!
//end!
try (final var sample = new Sample()) {
throw new IllegalStateException();
} catch (IllegalStateException e) {
System.out.println("IllegalStateException!");
}
// Result
// ↓
//close : called!
//IllegalStateException!
Methods
void close ()
关闭此资源，放弃所有底层资源。 (机器翻译)
final var file = Path.of("R:", "java-work", "test.txt");
System.out.println(file); // R:\java-work\test.txt
try (final var writer = Files.newBufferedWriter(file)) {
writer.write("abcd");
}
final var str = Files.readString(file);
System.out.println(str); // abcd
final var url = URI.create("http://example.com").toURL();
try (final var reader = new BufferedReader(
new InputStreamReader(url.openStream()))) {
reader.lines().forEach(System.out::println);
}
// Result
// ↓
//<!doctype html>
//<html>
//<head>
// <title>Example Domain</title>
// ...
//</html>
final var file = Path.of("R:", "java-work", "test.txt");
// An example without a try-with-resources statement.
final var writer = Files.newBufferedWriter(file);
try {
writer.write("abcd");
} finally {
writer.close();
}
final var str = Files.readString(file);
System.out.println(str); // abcd