java 常用API 时间

package com.orcal.demc01;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class Sj {

	public static void main(String[] args) throws ParseException {
		// TODO Auto-generated method stub
       method1();
       method2();
       method3();
	}
    public static void method1(){
    	//日期格式化对象
    	SimpleDateFormat sdf=new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
    	//将日期对象转换成字符串
    	Date d=new Date();
    	String date=sdf.format(d);
    	System.out.println(date);
    }
    public static void method2() throws ParseException{
    	//将字符串转换成日期对象
    	SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd");
    	String date="1992-02-02";
    	Date d=sdf.parse(date);
    	System.out.println(d);
    }
    public static void method3(){
    	//日历类
    	Calendar c=Calendar.getInstance();
    	System.out.println(c);
    	System.out.println(c.get(Calendar.YEAR));
    	System.out.println(c.get(Calendar.DAY_OF_WEEK));
    	System.out.println(c.get(Calendar.MONTH));
    	System.out.println(c.get(Calendar.DATE));
    	c.add(Calendar.DATE,3);
		System.out.println(c.get(Calendar.DATE));
		//将日历类转换成日期对象
		Date d=c.getTime();
		System.out.println(d);
		//设置指定日期
		c.set(Calendar.YEAR, 2099);
		c.set(Calendar.MONTH, 6);
		c.set(Calendar.DATE, 6);
		c.set(2055, 6,7);
		System.out.println(c.get(Calendar.YEAR));}

	public static void a(){
		//创建今天的日历类对象
		long today=System.currentTimeMillis();
		//创建我出生的日期
		Calendar birth=Calendar.getInstance();
		birth.set(2000,11,31);
		//转换日期类对象
		Date b=birth.getTime();
		//获取出生那天的毫秒值
		long bir=b.getTime();
		//我活了多少毫秒值
		long cha=(today-bir)/1000/60/60/24;
		System.out.println(cha);
	}

}