java - 哪个 close() 先运行？

Question

如果我有多个资源，在 try catch 中，哪个先关闭？

public class TestRes {
  public static void main(String[] args) {
    TestRes tr = new TestRes();
    tr.test();
  }

  public void test() {
    try (MyResource1 r1 = new MyResource1(); MyResource2 r2 = new MyResource2(); ) {
       System.out.print("T ");
    } catch (IOException ioe) {
      System.out.print("IOE ");
    } finally {
      System.out.print("F ");
    }
  }

  class MyResource1 implements AutoCloseable {
    public void close() throws IOException {
      System.out.print("1 ");
    }
  }

  class MyResource2 implements Closeable {
    public void close() throws IOException {
      throw new IOException();
    }
  }
}

此示例输出:

T 1 IOE F 

如果我改变顺序，那么...

public class TestRes {
  public static void main(String[] args) {
    TestRes tr = new TestRes();
    tr.test();
  }

  public void test() {
    try (MyResource2 r2 = new MyResource2(); MyResource1 r1 = new MyResource1();) {
       System.out.print("T ");
    } catch (IOException ioe) {
      System.out.print("IOE ");
    } finally {
      System.out.print("F ");
    }
  }

  class MyResource1 implements AutoCloseable {
    public void close() throws IOException {
      System.out.print("1 ");
    }
  }

  class MyResource2 implements Closeable {
    public void close() throws IOException {
      throw new IOException();
    }
  }
}

我得到相同的输出 - 为什么？

Answer 1

您似乎认为 close() 方法的异常会阻止调用其他 close() 方法。这是错误的。

Java 语言规范，部分 14.20.3. try-with-resources , 说:

Resources are closed in the reverse order from that in which they were initialized. A resource is closed only if it initialized to a non-null value. An exception from the closing of one resource does not prevent the closing of other resources. Such an exception is suppressed if an exception was thrown previously by an initializer, the try block, or the closing of a resource.

这意味着 close() 方法打印 1 将始终执行，第一部分回答您的 “哪个 close() 先运行？” 问题。