java ctrl+c(kill 2)打断过程

本文主要介绍用ctrl+c打断java进程后的情况

• 没有shutdown hook
• 存在shutdown hook

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当程序不存在shutdown hook的时候

程序会直接退出，即使有线程在跑，也不会产生任何打断信号给线程，例如：

 public class BB{        public static void main(String[] args) {            Thread t = new Thread(new Runnable() {                @Override                public void run() {                    while (true) {                        try {                            Thread.sleep(1000);                        } catch (InterruptedException e) {                            Thread.currentThread().interrupt();                        }                    }                }            });            t.start();            while(true) {                 try {                    Thread.sleep(1000);                } catch (InterruptedException e) {                    Thread.currentThread().interrupt();                    System.out.println("interrupted.");                }            }        }}

程序会直接推出，进程资源被回收。

当存在shutdown hook的情况

有shutdownhook，shutdownhook结束后，即使有进程没有结束，进程还是会退出，例如：

public class AA {        public static void main(String[] args) {        Thread aaa = new Thread(new Runnable() {            @Override            public void run() {                while (true) {                    try {                        Thread.sleep(1000);                    } catch (InterruptedException e) {                        Thread.currentThread().interrupt();                        System.out.println("interrupted.");                    }                }            }        });        Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {            @Override            public void run() {        }            }        }, "Data"));        aaa.start();        }}

ctrl+c打断后执行shutdown hook，hook时空的，所以很快结束，上面的线程被系统回收。我们正常情况下是在hook中打断线程，并作join操作，做好善后处理：

public class AA {        public static void main(String[] args) {                Thread aaa = new Thread(new Runnable() {            @Override            public void run() {                while (!Thread.interrupted()) {                    try {                        Thread.sleep(1000);                    } catch (InterruptedException e) {                        Thread.currentThread().interrupt();                        System.out.println("interrupted.");                    }                }            }        });        Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {            @Override            public void run() {                try{                aaa.interrupt();                aaa.join();                } catch (InterruptedException e) {            System.out.println("hhh");            Thread.currentThread().interrupt();        }            }        }, "Data"));        aaa.start();        }}

此时ctrl+c打断后会县打断线程，线程结束后，这个shutdown hook结束，进程结束。