Calendar calendar = Calendar.getInstance();
Date date = calendar.getTime();

// 加一天
calendar.add(Calendar.DAY_OF_MONTH, 1);
// 減一天
calendar.add(Calendar.DAY_OF_MONTH, -1);
// 加一小時(shí)
calendar.add(Calendar.HOUR_OF_DAY, 1);
// 減一小時(shí)
calendar.add(Calendar.HOUR_OF_DAY, -1);
// 加一分鐘
calendar.add(Calendar.MINUTE, 1);
// 減一分鐘
calendar.add(Calendar.MINUTE, -1);

// 獲取年份
int year = calendar.get(Calendar.YEAR);
// 獲取月份（注意：月份從0開(kāi)始，所以需要加1）
int month = calendar.get(Calendar.MONTH) + 1;
// 獲取日期
int day = calendar.get(Calendar.DAY_OF_MONTH);
// 獲取小時(shí)
int hour = calendar.get(Calendar.HOUR_OF_DAY);
// 獲取分鐘
int minute = calendar.get(Calendar.MINUTE);
// 獲取秒
int second = calendar.get(Calendar.SECOND);

// 獲取當(dāng)前月份的最大天數(shù)
int maxDay = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);

		Date date = new Date();
 
		SimpleDateFormat spf = new SimpleDateFormat("yyyy年-MM月-dd日:HH時(shí)-mm分-ss秒");
 
		System.out.println(spf.format(date));

        //輸出為:
        
        2021年-7月-14日:17時(shí)-15分-53秒

package com.hp.date;

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

public class CalendarDemo{
    public static void main(String[] args) throws Exception {
        //獲取獲取系統(tǒng)的當(dāng)前日歷對(duì)象
        Calendar instance = Calendar.getInstance();

        //1、獲取今天是周幾
        int weekDay = instance.get(Calendar.DAY_OF_WEEK);
        System.out.println("今天是周:" + (weekDay - 1));

        //2、獲取系統(tǒng)當(dāng)前年
        int year = instance.get(Calendar.YEAR);
        System.out.println("今年是:" + year + "年");

        //3、獲取系統(tǒng)當(dāng)前月
        int month = instance.get(Calendar.MONTH);
        System.out.println("本月是:" + (month + 1) + "月");

        //4、獲取系統(tǒng)當(dāng)前日
        int day = instance.get(Calendar.DATE);
        System.out.println("今天是" + day + "號(hào)");

        //5、獲取上午跟下午
        int am_pm = instance.get(Calendar.AM_PM);
        if (am_pm == 0)
            System.out.println("是上午");
        else
            System.out.println("是下午");

        //6、獲取當(dāng)前的系統(tǒng)時(shí)間[date-->String]的過(guò)程
        Date time = instance.getTime();//獲取的是當(dāng)前系統(tǒng)的時(shí)間
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss SSS");
        String showTime = format.format(time);
        System.out.println("當(dāng)前系統(tǒng)時(shí)間為：" + showTime);

        //7、自定義日歷的時(shí)間
        String strTime = "2021-07-07";
        Date date = new SimpleDateFormat("yyyy-MM-dd").parse(strTime);
        instance.setTime(date);//將時(shí)間對(duì)象data設(shè)置為新的日歷
        System.out.println("修改后的系統(tǒng)時(shí)間為：" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss SSS").format(instance.getTime()));
    }
    
  		System.out.println("------------Calendar和Date轉(zhuǎn)換------------");
        Date now = calendar.getTime();
        calendar.setTime(now);


        System.out.println("------------Calendar日期計(jì)算以及判斷------------");
        calendar = new GregorianCalendar();
        Calendar calendar2 = new GregorianCalendar();
        calendar2.set(Calendar.YEAR, 2800);
        //是否在某個(gè)時(shí)間(calendar2)之后
        System.out.println(calendar.after(calendar2));
        //是否在某個(gè)時(shí)間(calendar2)之前
        System.out.println(calendar.before(calendar2));
        //增加多少年年，月日以及時(shí)分秒同理
        calendar.add(Calendar.YEAR, -10);

    } 
}

同時(shí)在調(diào)用parse這個(gè)方法時(shí)，會(huì)出現(xiàn)異常，
try {

}    catch (ParseException e) {
e.printStackTrace();
}