Java关闭钩子 [英] Java shutdown hook

问题描述

我已将以下代码添加到我的程序中：

I have added the following code to my program:

Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {
    @Override
    public void run() {
        System.out.println("exit");
    }
}){});

但是我看不到这条消息。附加信息：我正在Netbeans IDE中运行程序。

I however do not see the message. Additional information: I am running the program from inside Netbeans IDE.

编辑：我忘了添加一个全局线程来保持程序活着。我按下Netbeans右下角的[x]来关闭它。

I forgot to add that there is a global Thread that keeps the program alive. I close it by pressing the [x] in Netbeans lower right corner.

推荐答案

JVM可以有序或突然关闭方式。关闭挂钩运行以便有序关闭：当最后一个正常线程终止时，有人调用 System.exit 或其他特定于平台的方法（例如键入Ctrl-C）。

The JVM can shutdown in either an orderly or abrupt manner. A shutdown hook runs for an orderly shutdown: when the last normal thread terminates, someone calls System.exit or by other platform specific means (such as typing Ctrl-C).

关闭挂钩将不会因JVM的突然关闭而运行。当你按下Netbeans右下角的[x]时，这将导致JVM突然关闭，这就是没有启动关闭钩子的原因。

Shutdown hooks will not run for an abrupt shutdown of the JVM. As you are pressing the [x] in Netbeans lower right corner, this will cause an abrupt shutdown of the JVM and this is why the shutdown hook was not started.

For示例：

public class ShutdownHook {
public void attachShutDownHook() {
    Runtime.getRuntime().addShutdownHook(new Thread() {
        @Override
        public void run() {
            System.out.println("exit");
        }
    });

}

public static void main(String[] args) {
    ShutdownHook sample = new ShutdownHook();
    sample.attachShutDownHook();
    try {
        Thread.sleep(3000);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

}

如果您运行上面的代码，并让程序正常完成，您将在控制台上看到 exit 。但是如果你按[x]（在3秒内）突然关闭它，关机挂钩将不会运行，并且控制台上不会打印任何退出。

If you run the above code, and let the program complete normally, you will see exit printed on the console. But if you press [x] (within 3 secs) to close it abruptly, the shutdown hook will not run and there will not be any exit printed on the console.

这篇关于Java关闭钩子的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！