java SimpleDateFormat使用方法

import java.io.*;
import java.util.*;
import java.text.*;

public class tmp
{
        public static void main(String args[]) throws Exception
        {
                DateFormat df = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");

                String str = df.format(new Date()); /* convert date to string */
                System.out.println(str);

                Date date = df.parse(str); /* convert string to date */
                System.out.println(date);
        }
}