Runtime.getRuntime().addShutdownHook

场景：如果希望，在jvm关闭时，先执行内存回收，对象销毁，先处理其他非守护线程，不处理某个线程，等到最后关闭jvm时才处理此线程

用法：定义一个线程方法，在jvm关闭之前执行此方法

代码实例：

public static void main(String[] args) {
   Thread hookThread = new Thread() {
      public void run() {
         System.out.println("Run hookThread...");
      }
   };
   Runtime.getRuntime().addShutdownHook(hookThread);
   Runnable task1 = new Runnable() {
      public void run() {
         try {
            Thread.sleep(1000);
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
         System.out.println("Run task1...gogogo");
      }
   };
   Runnable task2 = new Thread() {
      public void run() {
         try {
            Thread.sleep(500);
         } catch (InterruptedException e) {
            e.printStackTrace();
         }
         System.out.println("Run task2...gogogo");
      }
   };
   task1.run();
   task2.run();
}

结果：

Run task1...gogogo
Run task2...gogogo
Run hookThread...