源地址：http://kim-miao.iteye.com/blog/1662550

void java.lang.Runtime.addShutdownHook(Thread hook)

该方法用来在jvm中增加一个关闭的钩子。当程序正常退出,系统调用 System.exit方法或虚拟机被关闭时才会执行添加的shutdownHook线程。其中shutdownHook是一个已初始化但并不有启动的线程，当jvm关闭的时候，会执行系统中已经设置的所有通过方法addShutdownHook添加的钩子，当系统执行完这些钩子后，jvm才会关闭。所以可通过这些钩子在jvm关闭的时候进行内存清理、资源回收等工作。  

 

public class TestRuntimeShutdownHook {      public static void main(String[] args) {            Thread shutdownHookOne = new Thread() {              public void run() {                  System.out.println("shutdownHook one...");              }          };          Runtime.getRuntime().addShutdownHook(shutdownHookOne);            Runnable threadOne = new Runnable() {              public void run() {                  try {                      Thread.sleep(1000);                  } catch (InterruptedException e) {                      e.printStackTrace();                  }                  System.out.println("thread one doing something...");              }          };            Runnable threadTwo = new Thread() {              public void run() {                  try {                      Thread.sleep(2000);                  } catch (InterruptedException e) {                      e.printStackTrace();                  }                  System.out.println("thread two doing something...");              }          };            threadOne.run();          threadTwo.run();      }  }