推荐Calendar操作日期

package com.example.demo.Calender;

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

public class CalenderController {

    public static void main(String[] args){
        System.out.println(getPastDate(1));
        System.out.println(getPastMonth(2));
    }

    // 当前日期之前几天
    private static String getPastDate(int past) {
        Calendar calender = Calendar.getInstance();
        calender.set(Calendar.DATE, calender.get(Calendar.DATE) - past);
        Date today = calender.getTime();
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
        String result = simpleDateFormat.format(today);
        return result;
    }

    // 当前日期之前几月（同理年，秒，分钟）
    private static String getPastMonth(int month) {
        Calendar calendar = Calendar.getInstance();
        calendar.set(Calendar.MONTH, calendar.get(Calendar.MONTH) - month);
        Date today = calendar.getTime();
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
        String result = simpleDateFormat.format(today);
        return result;
    }
}

package com.example.demo.Calender;

import org.junit.Before;
import org.junit.Test;

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

public class CalendarDemo {
    Calendar calendar = null;

    @Before
    public void test(){
        calendar = Calendar.getInstance();
    }

    /**
     * Calendar 的月份从0开始 = 实际月份 - 1
     */
    @Test
    public void test1() {
        System.out.println(calendar.get(Calendar.MONTH));
        calendar.set(Calendar.MONTH, calendar.get(Calendar.MONTH) - 2);
        System.out.println(calendar.get(Calendar.MONTH));
        Date today = calendar.getTime();
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
        String result = simpleDateFormat.format(today);
        System.out.println(result);
    }

}