java 操作实例

1、日期的加减操作

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

public class DateCalculate {

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

    /**
     * 获取形如yyyy-MM-dd HH:mm:ss
     * @param date
     * @return
     */
    public static String datetimeToString(Date date) {
        return sdf.format(date);
    }

    /**
     * 根据时间字符串获取日期
     * @param dateString
     * @return
     * @throws ParseException
     */
    public static Date stringToDatetime(String dateString) throws ParseException {
        return sdf.parse(dateString);
    }

    /**
     * 获取本月最后一天
     * @return
     */
    public static Date getMonthStartDate(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.set(Calendar.DAY_OF_MONTH,1);
        return calendar.getTime();
    }

    /**
     * 获取本月最后一天
     * @return
     */
    public static Date getMonthEndDate(Date date) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.set(Calendar.DAY_OF_MONTH,calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
        return calendar.getTime();
    }

    /**
     * 获取指定日期所属周的开始时间
     * @param date
     * @return
     */
    public static Date getBeginWeekDate(Date date) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        int dayOfWeek = cal.get(Calendar.DAY_OF_WEEK);
        if (dayOfWeek == 1) {
            dayOfWeek += 7;
        }
        cal.add(Calendar.DATE,2 - dayOfWeek);
        return cal.getTime();
    }

    /**
     * 距离指定日期所属周结束时间
     * @return
     */
    public static Date getEndWeekDate(Date date) {
        Calendar cal = Calendar.getInstance();
        cal.setTime(date);
        int dayOfWeek = cal.get(Calendar.DAY_OF_WEEK);
        if (dayOfWeek == 1) {
            dayOfWeek += 7;
        }
        cal.add(Calendar.DATE,8 - dayOfWeek);
        return cal.getTime();
    }

    /**
     * 对指定日期进行年份加减操作
     * @param date
     * @param num
     * @return
     */
    public static Date calculateDateOfYear(Date date,Integer num) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.add(Calendar.YEAR,num);
        return calendar.getTime();
    }

    /**
     * 对指定日期月份进行加减操作
     * @param date
     * @param num
     * @return
     */
    public static Date calculateDateOfMonth(Date date,Integer num) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.add(Calendar.MONTH,num);
        return calendar.getTime();
    }

    /**
     * 对指定日期天数进行加减操作
     * @param date
     * @param num 负整数 正整数
     * @return
     */
    public static Date calculateDateOfDay(Date date,Integer num) {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(date);
        calendar.add(Calendar.DAY_OF_MONTH,num);
        return calendar.getTime();
    }

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

        System.out.println(datetimeToString(getMonthStartDate(sdf.parse("2019-12-04 12:09:52"))));
        System.out.println(datetimeToString(getEndWeekDate(sdf.parse("2019-12-04 12:09:52"))));
        System.out.println(datetimeToString(calculateDateOfYear(stringToDatetime("2019-12-04 12:09:52"),-2)));
    }
}　　

原文地址：https://www.cnblogs.com/snow-wolf-1/p/12001370.html