date转long 和long转date

import java.text.SimpleDateFormat;

import java.util.Date;

public class T {

public static void main(String[] args) throws Exception {

SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

long timeStart=sdf.parse("2011-09-20 12:30:45").getTime();

System.out.println(timeStart);

Date date = new Date(timeStart);

System.out.println(sdf.format(date));

}