LocalDateTime简单使用

ゝ一纸荒年。 2022-08-30 11:57 195阅读 0赞

现象：  
LocalDateTime API 简单使用  
方法：  
JDK8新特性里提供了3个时间类：LocalDate、LocalTime、LocalDateTime

一：LocalDate的使用

// 获取当前日期
        LocalDate now = LocalDate.now();
        System.out.println("当前时间:"+now);
        //当前时间:2021-07-20
    
        // 设置指定日期
        LocalDate localDate = LocalDate.of(2021, 7, 22);
        System.out.println("输出时间:"+localDate);
        //输出时间:2021-07-22
    
        // 获取年
        int year = localDate.getYear();
        System.out.println("获取年:"+year);
        //获取年:2021
    
        // 获取月
        Month month = localDate.getMonth();
        int month1 = localDate.get(ChronoField.MONTH_OF_YEAR);
        System.out.println("获取月:"+month1);
        //获取月:7
    
        // 获取日
        int day = localDate.getDayOfMonth();
        int day1 = localDate.get(ChronoField.DAY_OF_MONTH);
        System.out.println("获取日:"+day1);
        //获取日:22
    
        // 获取星期
        DayOfWeek dayOfWeek = localDate.getDayOfWeek();
        System.out.printf("获取星期:"+dayOfWeek);
        //获取星期:THURSDAY
        int dayOfWeek1 = localDate.get(ChronoField.DAY_OF_WEEK);
        System.out.printf("获取星期:"+dayOfWeek1);
        //获取星期:4

二：LocalTime 的使用

// 获取当前时间
     LocalTime now = LocalTime.now();
     System.out.println("当前时间:" + now);
     //当前时间:16:43:34.748
    
     LocalTime localTime = LocalTime.of(14, 20, 10);
     System.out.println("设置时间:" + localTime);
     //设置时间:14:20:10
    
     //获取小时
     int hour = localTime.getHour();
     System.out.println("获取小时:" + hour);
     //获取小时:14
     int hour1 = localTime.get(ChronoField.HOUR_OF_DAY);
     System.out.println("获取小时:" + hour1);
     //获取小时:14
    
     //获取分
     int minute = localTime.getMinute();
     System.out.println("获取分:" + minute);
     //获取分:20
     int minute1 = localTime.get(ChronoField.MINUTE_OF_HOUR);
     System.out.println("获取分:" + minute1);
     //获取分:20
    
     //获取秒
     int second = localTime.getSecond();
     System.out.println("获取秒:" + second);
     //获取秒:10
     int second1 = localTime.get(ChronoField.SECOND_OF_MINUTE);
     System.out.println("获取秒:" + second1);
     //获取秒:10

三：LocalDateTime的使用

// 获取当前日期时间
    LocalDateTime localDateTime = LocalDateTime.now();
    System.out.println("当前日期时间："+localDateTime);
    //当前日期时间：2021-07-21T16:53:12.281
    
    // 设置日期
    LocalDateTime localDateTime1 = LocalDateTime.of(2021, Month.SEPTEMBER, 10, 14, 46, 56);
    System.out.println("设置日期时间："+localDateTime1);
    //设置日期时间：2021-09-10T14:46:56
    
    LocalDate localDate = LocalDate.of(2021, 7, 22);
    LocalTime localTime = LocalTime.of(12, 20, 10);
    LocalDateTime localDateTime2 = LocalDateTime.of(localDate, localTime);
    System.out.println("设置日期时间："+localDateTime2);
    //设置日期时间：2021-07-22T12:20:10
    
    LocalDateTime localDateTime3 = localDate.atTime(localTime);
    System.out.println("日期设置时间："+localDateTime3);
    //日期设置时间：2021-07-22T12:20:10
    
    LocalDateTime localDateTime4 = localTime.atDate(localDate);
    System.out.println("时间设置日期："+localDateTime4);
    //时间设置日期：2021-07-22T12:20:10
    
    // 获取LocalDate
    LocalDate localDate2 = localDateTime.toLocalDate();
    System.out.println("获取LocalDate："+localDate2);
    //获取LocalDate：2021-07-21
    
    // 获取LocalTime
    LocalTime localTime2 = localDateTime.toLocalTime();
    System.out.println("获取LocalTime："+localTime2);
    //获取LocalTime：16:53:42.553

四：LocalDate、LocalTime、LocalDateTime、Instant为不可变对象，修改这些对象对象会返回一个副本。

1、增加、年数、月数、天数等使用plus方法  
![在这里插入图片描述][5a9d72f6993f25a76245819a838e809c.png_pic_center]

LocalDateTime localDateTime = LocalDateTime.of(2021, Month.JULY, 21, 14, 46, 56);
     System.out.println("设置日期时间："+localDateTime);
     //当前日期时间：2021-07-21T14:46:56
    
     //增加一年
     LocalDateTime localDateTime1 = localDateTime.plusYears(1);
     System.out.println(""+localDateTime1);
     //2022-07-21T14:46:56
     LocalDateTime localDateTime2 = localDateTime.plus(1, ChronoUnit.YEARS);
     System.out.println(""+localDateTime2);
     //2022-07-21T14:46:56
    
     //增加5天
     LocalDateTime localDateTime3 = localDateTime.plusDays(5);
     System.out.println(""+localDateTime3);
     //2021-07-26T14:46:56
     LocalDateTime localDateTime4 = localDateTime.plus(5, ChronoUnit.DAYS);
     System.out.println(""+localDateTime4);
     //2021-07-26T14:46:56

2、减少、年数、月数、天数等使用minus方法  
![在这里插入图片描述][b142283a20111462337f2a18e98f4657.png_pic_center]

LocalDateTime localDateTime = LocalDateTime.of(2021, Month.JULY, 21, 14, 46, 56);
    System.out.println("设置日期时间："+localDateTime);
    //设置日期时间：2021-07-21T14:46:56
    
    //减少2个月
    LocalDateTime localDateTime1 = localDateTime.minusMonths(2);
    System.out.println(String.valueOf(localDateTime1));
    //结果： 2021-05-21T14:46:56
    
    LocalDateTime localDateTime2 = localDateTime.minus(2, ChronoUnit.MONTHS);
    System.out.println(String.valueOf(localDateTime2));
    //结果： 2021-05-21T14:46:56
    
    //减少2秒
    LocalDateTime localDateTime3 = localDateTime.minusSeconds(2);
    System.out.println(String.valueOf(localDateTime3));
    //结果： 2021-07-21T14:46:54
    
    LocalDateTime localDateTime4 = localDateTime.minus(2, ChronoUnit.SECONDS);
    System.out.println(String.valueOf(localDateTime4));
    //结果：2021-07-21T14:46:54

3、修改年月日时分秒通过with  
![在这里插入图片描述][f449062530c22a9dcdcfdb174a78648e.png_pic_center]

LocalDateTime localDateTime = LocalDateTime.of(2021, Month.JULY, 21, 14, 46, 56);
     System.out.println("设置日期时间："+localDateTime);
     //设置日期时间：2021-07-21T14:46:56
    
     LocalDateTime localDateTime1 = localDateTime.withYear(2011);
     System.out.println(localDateTime1);
     //2011-07-21T14:46:56
    
     LocalDateTime localDateTime2 = localDateTime.withHour(5);
     System.out.println(localDateTime2);
     //2021-07-21T05:46:56

4、格式化时间

LocalDateTime localDateTime = LocalDateTime.of(2021, Month.JULY, 21, 14, 46, 56);
    System.out.println("设置日期时间："+localDateTime);
    //设置日期时间：2021-07-21T14:46:56
    
    String time1 = localDateTime.format(DateTimeFormatter.BASIC_ISO_DATE);
    System.out.println(time1);
    //20210721
    
    String time2 = localDateTime.format(DateTimeFormatter.ISO_LOCAL_DATE);
    System.out.println(time2);
    //2021-07-21
    
    String time3 = localDateTime.format(DateTimeFormatter.ISO_LOCAL_TIME);
    System.out.println(time3);
    //14:46:56
    
    String time4 = localDateTime.format(DateTimeFormatter.ISO_DATE_TIME);
    System.out.println(time4);
    //2021-07-21T14:46:56
    
    //自定义格式化
    DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd hh:mm:ss");
    String time8 = localDateTime.format(dateTimeFormatter);
    System.out.println(time8);
    //2021-07-21 02:46:56

5、时间比较使用 isAfter \\ isBefore

LocalDateTime localDateTime = LocalDateTime.of(2021, Month.JULY, 21, 14, 46, 56);
    System.out.println("设置日期时间："+localDateTime);
    //设置日期时间：2021-07-21T14:46:56
    
    LocalDateTime localDateTime1 = LocalDateTime.of(2021, Month.JULY, 21, 15, 46, 56);
    System.out.println("设置日期时间："+localDateTime1);
    //设置日期时间：2021-07-21T14:46:56
    
    System.out.println(localDateTime.isAfter(localDateTime1));
    System.out.println(localDateTime.isBefore(localDateTime1));

6、与Date的转换

LocalDateTime localDateTime = LocalDateTime.of(2021, Month.JULY, 21, 14, 46, 56);
     System.out.println("设置日期时间：" + localDateTime);
     //设置日期时间：2021-07-21T14:46:56
    
     //转换为时间戳
     ZoneId zoneId = ZoneId.systemDefault();
     Instant instant = localDateTime.atZone(zoneId).toInstant();
     System.out.println(instant.toEpochMilli());
     //1626850016000
    
     //时间戳转LocalDateTime
     Instant instant1 = Instant.ofEpochMilli(1626850016000L);
     ZoneId zone1 = ZoneId.systemDefault();
     LocalDateTime localDateTime1 = LocalDateTime.ofInstant(instant1, zone1);
     System.out.println(localDateTime1);
     //2021-07-21T14:46:56
    
     //Date转LocalDateTime
     Date date = new Date();
     Instant instant2 = date.toInstant();
     ZoneId zoneId2 = ZoneId.systemDefault();
     LocalDateTime localDateTime2 = instant2.atZone(zoneId2).toLocalDateTime();
     System.out.println(localDateTime2);
     // 2021-07-21T19:56:42.387
    
     // LocalDateTime转Date
     ZoneId zoneId3 = ZoneId.systemDefault();
     ZonedDateTime zdt3 = localDateTime.atZone(zoneId3);
     Date from3 = Date.from(zdt3.toInstant());
     System.out.println(from3);
     //Wed Jul 21 14:46:56 CST 2021

[5a9d72f6993f25a76245819a838e809c.png_pic_center]: /images/20220829/99ffe9df569546cfb1b1fa08a3fa6e3f.png
[b142283a20111462337f2a18e98f4657.png_pic_center]: /images/20220829/a47d30a93dd343918109d3e76c28cd69.png
[f449062530c22a9dcdcfdb174a78648e.png_pic_center]: /images/20220829/4176449f854c405fa54f7c86139d7abf.png