Date类和Calendar类

package com.wang.date;

import java.util.Date;

public class DateDemo {
    public static void main(String[] args) {
        //测试date类
        //测试空参构造，采用当前系统的默认时间
        Date date=new Date();
        System.out.println("date:"+date);
        //获取当前操作系统的毫秒值
        long time=date.getTime();
        System.out.println("time:"+time);
        //date:Thu Oct 31 15:10:32 CST 2019
        //time:1572505832089
        //创建指定的时间
        Date date1=new Date(1572505832089L);
        System.out.println("date1:"+date1);
    }
}

package com.wang.date;

import java.util.Calendar;

public class CalendarDemo {
    public static void main(String[] args) {
        //Calendar calendar=new Calendar();Calendar是抽象类，不能实例化
       //static Calendar getInstance():根据当前系统时区和语言环境获取日历对象
        Calendar calendar=Calendar.getInstance();
        System.out.println(calendar);
      //int get(int field):返回给定日历字段的值
       //获取年月日的信息
        int year=calendar.get(Calendar.YEAR);
        int month=calendar.get(Calendar.MONTH);//java中用0-11表示月份
        int day=calendar.get(Calendar.DAY_OF_MONTH);
        System.out.println(year+"年"+(month+1)+"月"+day+"日");
      //void set(int field,int value):将给定的日历字段设置为指定的值
        //设置指定时间2022年2月2日
        calendar.set(Calendar.YEAR,2022);
        int year1=calendar.get(Calendar.YEAR);
        calendar.set(Calendar.MONTH,2);
        int month1=calendar.get(Calendar.MONTH);
        calendar.set(Calendar.DAY_OF_MONTH,2);
        int day1=calendar.get(Calendar.DAY_OF_MONTH);
        System.out.println(year1+"年"+month1+"月"+day1+"日");
        System.out.println("============================================");
        calendar.set(2023,3,4);
        int year2=calendar.get(Calendar.YEAR);
        int month2=calendar.get(Calendar.MONTH);
        int day2=calendar.get(Calendar.DAY_OF_MONTH);
        System.out.println(year2+"年"+month2+"月"+day2+"日");
    }
}