为主程序增加Hook，监控主线程的退出

public class ThreadHookTest {


public static void main(String[] args) {

System.out.println("end end");

//增加hook

Runtime.getRuntime().addShutdownHook(new ShutdownHook());

System.out.println("main end");
Thread t = new Thread(new Runnable(){
@Override
public void run() {
int i=0;
while(i<100){
System.out.println(i++);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
});
t.start();
}

static class ShutdownHook extends Thread{


@Override
public void run() {
System.out.println("============shutdown================");
}

}

}

当线程 t 执行完毕后，调用ShutdownHook ，打印“============shutdown================”