DateTime相关内容

由于SimpledataFormat线程是线程非安全的,因此在JAVA8以后使用DateTimeFormatter，JAVA8以前使用threadlocal,joda-time也是需要的

<dependency>
  <groupId>joda-time</groupId>
  <artifactId>joda-time</artifactId>
  <version>2.9.2</version>
</dependency>

获取当前时间戳

    LocalDateTime currentTime = LocalDateTime.now();
    System.out.println("当前时间: " + currentTime);
    
    结果:当前时间: 2021-09-06T22:16:24.440

获取当前时间

      LocalTime localTime = LocalTime.now();
      System.out.println(localTime);
    
    结果:当前时间: 22:17:50.403

格式化日期时间类型为字符串

    LocalDateTime localDateTime=LocalDateTime.now();
    //格式化日期时间类型为字符串
    DateTimeFormatter dateTimeFormatter=DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    String ss = dateTimeFormatter.format(localDateTime).toString();
    System.out.println(ss);

    结果: 当前时间: 2021-09-06 22:20:58

日期时间转换为LocalDateTime

    DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");
        LocalDateTime yy = LocalDateTime.parse("2021-09-06 21:22:33.555", df);
        System.out.println(yy);

    结果: 2021-09-25T21:22:33.555

日期String转换为LocalDateTime

    DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");
        LocalDateTime yy = LocalDateTime.parse("2021-09-06 21:22:33.555", df);
        System.out.println(yy);

    结果: 2021-09-25T21:22:33.555

日期String转换为Long

DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");
//北京时间 +8
long tsBeijing= LocalDateTime.parse("2021-09-25 21:22:33.555", df).toInstant(ZoneOffset.ofHours(8)).toEpochMilli();
// UTC时间
long tsUTC= LocalDateTime.parse("2021-09-25 21:22:33.555", df).toInstant(ZoneOffset.UTC).toEpochMilli();

System.out.println("tsBeijing "+tsBeijing);
System.out.println("tsUTC "+tsUTC);
System.out.println((tsUTC-tsBeijing)/1000/3600);

结果：
tsBeijing 1632576153555
tsUTC 1632604953555
8

Long转换为String

 public void time3()
    {
        Long timeLong= 1632561753555L;
        String time="";
        String datePattern="yyyy-MM-dd HH:mm:ss.SSS";
        //北京时间 ofHours(8)
        LocalDateTime dateTimeOfBeijing = LocalDateTime.ofEpochSecond(timeLong/1000, 0, ZoneOffset.ofHours(8));
        //UTC时间 UTC
        LocalDateTime dateTimeOfUTC = LocalDateTime.ofEpochSecond(timeLong/1000, 0, ZoneOffset.UTC);
        String timeBeijing = dateTimeOfBeijing.format(DateTimeFormatter.ofPattern(datePattern));
        String timeUTC = dateTimeOfUTC.format(DateTimeFormatter.ofPattern(datePattern));
        System.out.println("timeBeijing "+timeBeijing);
        System.out.println("timeUTC "+timeUTC);
    }
}
      
结果:
timeBeijing 2021-09-25 17:22:33.000
timeUTC 2021-09-25 09:22:33.000

Long转换为String

Long timeLong = 1632561753555L;
String time = "";
String datePattern = "yyyy-MM-dd HH:mm:ss";
Instant ins = Instant.ofEpochSecond(timeLong / 1000);
String dataTime = ins.atZone(ZoneId.of("GMT")).toString();
System.out.println(dataTime);

      
结果:
2021-09-25T09:22:33Z[GMT]