java8 LocalDate和LocalDateTIme对日期时间的操作、LocalDate和String的相互转换、两个日期时间的插值计算等等

本文记录下LocalDate和LocalDateTime对日期的常用方法，日期的加减，两个日期时间的时间差，自定义时间格式formatter实现日期和String的相互转换

 注意until的两种写法计算不同的时间差值，详情可看如下注释和例子说明

package com.ssh.mydmx.common;

import lombok.extern.slf4j.Slf4j;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;

@Slf4j
public class LocalDateTest {

    private static final DateTimeFormatter FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd");
    private static final DateTimeFormatter DATE_TIME_FORMATTER = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");

    public static void main(String[] args) {
        //取当前时间
        LocalDate nowDate = LocalDate.now();
        LocalDateTime nowDataTime = LocalDateTime.now();

        //加30天
        LocalDate nowDatePlus30 = nowDate.plusDays(30L);
        LocalDateTime nowDateTimePlus30 = nowDataTime.plusDays(30L);

        //减5天
        LocalDate nowDateMinus5 = nowDate.minusDays(5L);
        LocalDateTime nowDateTimeMinus5 = nowDataTime.minusDays(5L);

        //定义formatter 也可选择根据自己需要格式，选择使用DateTimeFormatter里定义好的formatter
        //String---------->localDate
        LocalDate parseNowStr = LocalDate.parse("2021-12-31", FORMATTER);
        //localDate----->String
        log.info("localDate----->String={}",parseNowStr.format(FORMATTER));
        log.info("localDate----->String={}",nowDataTime.format(DATE_TIME_FORMATTER));

        //取两个时间差,实际天数差 例如date1-2022-01-30,date2=2021-12-26 时间差====35
        log.info("取时间差===={}",nowDateTimeMinus5.until(nowDateTimePlus30, ChronoUnit.DAYS));
        log.info("取时间差===={}",nowDateMinus5.until(nowDatePlus30,ChronoUnit.DAYS));

        //取两个时间差，只看日期 例如date1-2022-01-30,date2=2021-12-26 时间差====4
        int days = nowDateMinus5.until(nowDatePlus30).getDays();
        log.info("date1-{},date2={}取时间差===={}",nowDatePlus30.format(FORMATTER),nowDateMinus5.format(FORMATTER),days);

        //不足24小时不算一天 2021-12-30 15:51:29和2021-12-31 15:50:29 相差天数=0
        //同理不足一分钟也不算 比如6.4分钟算6分钟
        LocalDateTime demo1 = LocalDateTime.parse("2021-12-31 15:50:29", DATE_TIME_FORMATTER);
        LocalDateTime demo2 = LocalDateTime.parse("2021-12-30 15:51:29", DATE_TIME_FORMATTER);
        log.info("相差天数={}=分钟={}",demo2.until(demo1,ChronoUnit.DAYS),demo2.until(demo1,ChronoUnit.MINUTES));
    }
}