虚拟机关闭前的数据保存

public class Test {
 public Test() {
  java.lang.Runtime.getRuntime().addShutdownHook(new Thread() {
   public void run() {
    System.out.println("finished");
   }
  });
 }

 public static void sayHello() {
  System.out.println("hello");
 }

 public static void main(String[] args) {
  Test test = new Test();
  Test.sayHello();

 }

}