Java时间系列(JDK8)--LocalDate的使用

深藏阁楼爱情的钟 2023-10-01 03:22 19阅读 0赞

原文网址：[Java时间系列(JDK8)--LocalDate的使用\_IT利刃出鞘的博客-CSDN博客][Java_JDK8_--LocalDate_IT_-CSDN]

## 简介 ##

本文用示例介绍LocalDate的用法。LocalDate是JDK8新增的。

LocalDate与LocalDateTime的用法很接近。LocalDateTime详见：[Java时间系列(JDK8)--LocalDateTime的使用\_IT利刃出鞘的博客-CSDN博客\_IT利刃出鞘的博客-CSDN博客][Java_JDK8_--LocalDateTime_IT_-CSDN_IT_-CSDN]

## **常用操作** ##

### **日期差值** ###

**获取两个LocalDate的相差天数**

// 如果是 now.until(before, ChronoUnit.DAYS), 返回的结果是负数
    LocalDate before = LocalDate.of(2017, 9, 22);
    LocalDate now = LocalDate.now(ZoneId.systemDefault());
    long betweenDays = before.until(now, ChronoUnit.DAYS);

### Date互转 ###

**Date转LocalDate**

Date date = new Date();
    LocalDate localDate = Instant
    		.ofEpochMilli(date.getTime()).atZone(ZoneId.systemDefault())
    		.toLocalDate();

Date所在包：java.util.Date

**LocalDate转Date**

LocalDate localDate = LocalDate.now();
    Date date = Date.from(localDate
            .atStartOfDay()
            .atZone(ZoneId.systemDefault())
            .toInstant());

### 所有方法 ###

<table> 
 <tbody> 
  <tr> 
   <td><strong>方法</strong></td> 
   <td style="width:280px;"><strong>说明</strong></td> 
   <td style="width:109px;"><strong>示例结果</strong></td> 
  </tr> 
  <tr> 
   <td>LocalDate today = LocalDate.now();</td> 
   <td style="width:280px;">取当前日期</td> 
   <td style="width:109px;">2014-12-24</td> 
  </tr> 
  <tr> 
   <td>LocalDate crischristmas = LocalDate.of(2014, 12, 25);</td> 
   <td style="width:280px;">根据年月日取日期</td> 
   <td style="width:109px;">2014-12-25</td> 
  </tr> 
  <tr> 
   <td>LocalDate endOfFeb = LocalDate.parse("2014-02-28");</td> 
   <td style="width:280px;"> <p>根据字符串取。</p> <p>严格按照ISO yyyy-MM-dd验证，02写成2都不行。当然也有一个重载方法允许自己定义格式</p> </td> 
   <td style="width:109px;"></td> 
  </tr> 
  <tr> 
   <td>LocalDate firstDayOfThisMonth = today.with(TemporalAdjusters.firstDayOfMonth());</td> 
   <td style="width:280px;">取本月第1天</td> 
   <td style="width:109px;">2017-03-01</td> 
  </tr> 
  <tr> 
   <td> <p>LocalDate secondDayOfThisMonth =</p> <p>today.withDayOfMonth(2);</p> </td> 
   <td style="width:280px;">取本月第2天</td> 
   <td style="width:109px;">2017-03-02</td> 
  </tr> 
  <tr> 
   <td>LocalDate lastDayOfThisMonth = today.with(TemporalAdjusters.lastDayOfMonth());</td> 
   <td style="width:280px;">取本月最后一天，再也不用计算是28，29，30还是31</td> 
   <td style="width:109px;">2017-12-31</td> 
  </tr> 
  <tr> 
   <td>LocalDate firstDayOf2015 = lastDayOfThisMonth.plusDays(1);</td> 
   <td style="width:280px;">取下一天</td> 
   <td style="width:109px;"></td> 
  </tr> 
  <tr> 
   <td>LocalDate firstMondayOf2015 = LocalDate.parse("2017-01-01").with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY));</td> 
   <td style="width:280px;">取2017年1月第一个周一</td> 
   <td style="width:109px;"></td> 
  </tr> 
 </tbody> 
</table>

[Java_JDK8_--LocalDate_IT_-CSDN]: https://knife.blog.csdn.net/article/details/122772745
[Java_JDK8_--LocalDateTime_IT_-CSDN_IT_-CSDN]: https://knife.blog.csdn.net/article/details/120319901