Java使用勾子示例［转载］


import java.io.FileWriter;
import java.util.Date;

public class Runtimes {
    public Runtimes() {
        doShutDownWork();
    }
    //当应用程序在退出JVM的时候做一件事情。就是新开一个勾子程序过来处理

    private void doShutDownWork() {
        Runtime.getRuntime().addShutdownHook(new Thread(){
            @Override
            public void run() {
                try {
                    FileWriter fw = new FileWriter("c:\\t.log");
                    System.out.println("it is going to end");
                    fw.write("The app ended!" + (new Date().toString()));
                    fw.close();
                    System.gc();
                } catch (Exception e) {
                    // TODO: handle exception

                }
            }
        });
        
    }

    public static void main(String[] args) {
        Runtimes utils = new Runtimes();
        long s = System.currentTimeMillis();
        for (long i = 0; i < 2000000000; i++) {
            
        }
        long se = System.currentTimeMillis();
        System.out.println(se- s);
    }
}


笔记：如果要统计一段程序运行的时间长度是可以使用 System.currentTimeMillis(); 来捕获到的！