前言
在我们java开发中,Date日期这个字段会被经常使用,比如获取当前系统的时间,获取上个月,上一年的时间,以及获取两个日期相差的时分秒数,或者对日期类型进行格式化,等等,等等,下面将给大家详细介绍下Java中常用时间的一些相关方法
一、获取当前时间的方式
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public static void main(String[] args) {
//Date
Date now = new Date();
System.out.println(now);
//java8的时间
LocalDateTime localDateTime = LocalDateTime.now();
System.out.println(localDateTime);
Calendar calendar = Calendar.getInstance();
Date time = calendar.getTime();
System.out.println(time);
System.out.println( "年" + calendar.get(Calendar.YEAR));
System.out.println( "月" + (calendar.get(Calendar.MONTH) + 1 ));
//joda time
DateTime dateTime = DateTime.now();
System.out.println(dateTime);
}
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获取当前时间可以使用Date LocalDatetime Calendar Datetime
二、获取当月第n天
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public static void main(String[] args) {
//建议使用Calendar 可以设置年月日时分秒
Calendar calendar = Calendar.getInstance();
////当月16
calendar.set(Calendar.DAY_OF_MONTH, 16 );
System.out.println(calendar.getTime());
//当月16
DateTime now = DateTime.now();
DateTime dateTime = now.withDayOfMonth( 16 );
System.out.println(dateTime);
//当月14
LocalDateTime localDateTime = LocalDateTime.now();
System.out.println(localDateTime.withDayOfMonth( 14 ));
//1月11
System.out.println(localDateTime.withMonth( 1 ).withDayOfMonth( 11 ));
}
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三、格式化为字符串
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```
//使用SimpleDateFormat
SimpleDateFormat format = new SimpleDateFormat( "yyyy-MM-dd HH:mm:ss" );
System.out.println(format.format( new Date()));
//使用Calendar
Calendar calendar = Calendar.getInstance();
System.out.println(String.format( "%s年%s月%s日%s时%s分%s秒" , calendar.get(Calendar.YEAR),
calendar.get(Calendar.MONTH) + 1 , calendar.get(Calendar.DAY_OF_MONTH),
calendar.get(Calendar.HOUR_OF_DAY), calendar.get(Calendar.MINUTE), calendar.get(Calendar.SECOND)));
LocalDateTime now = LocalDateTime.now();
String str = now.format(DateTimeFormatter.ofPattern( "yyyy-MM-dd HH:mm:ss" ));
System.out.println(str);
```
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四、加减时间(单位可以是秒,小时等)
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public static void main(String[] args) {
Date now = new Date();
//加一小时
long time = now.getTime() + ( 60 * 60 * 1000 );
System.out.println( new Date(time));
/*
<dependency>
<groupId>cn.hutool</groupId>
<artifactId>hutool-all</artifactId>
<version>5.7.14</version>
</dependency>
*/
//引入Hutool 加一小时
System.out.println(DateUtil.offset(now, DateField.HOUR, 1 ));
//减一小时
System.out.println(DateUtil.offset(now, DateField.HOUR, - 1 ));
LocalDateTime localDateTime = LocalDateTime.now();
System.out.println( "加一小时" + localDateTime.plusHours( 1 ));
System.out.println( "减一小时" + localDateTime.minusHours( 1 ));
DateTime dateTime = DateTime.now();
System.out.println(dateTime.plusHours( 1 ));
System.out.println(dateTime.minusHours( 1 ));
}
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LocalDateTime和DateTime都自带增加和减少时间的方法
五、通过出生日期获取年龄
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public static void main(String[] args) {
//时间1990-12-05
DateTime birthDay = DateTime.now().withYear( 1990 ).withMonthOfYear( 10 ).withDayOfMonth( 23 );
System.out.println(birthDay);
//获取相差得年 会进行月份和日期比较 如
Years years = Years.yearsBetween(birthDay, new DateTime());
System.out.println(years);
System.out.println(years.getYears());
}
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还可以使用年份相减,再比较月,日的方法得到生日
六、判断两个时间段是否覆盖
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public static void main(String[] args) {
DateTime now = DateTime.now();
DateTime start1 = now;
DateTime end1 = now.plusMinutes( 1 );
DateTime start2 = now.plusSeconds( 50 );
DateTime end2 = now.plusMinutes( 2 );
Interval interval1 = new Interval(start1, end1);
Interval interval2 = new Interval(start2, end2);
System.out.println(interval1.overlaps(interval2));
System.out.println(start1.getMillis() < end2.getMillis() && start2.getMillis() < end1.getMillis());
}
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七、求两个时间间隔
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public static void main(String[] args) {
DateTime now = DateTime.now();
//开始时间
Date startTime = now.toDate();
//结束时间
Date endTime = now.plusHours( 1 ).toDate();
//1小时
System.out.println( "开始时间与结束时间的时间间隔:" + DateUtil.between(startTime, endTime, DateUnit.SECOND));
long time = (endTime.getTime() - startTime.getTime()) / 1000 ;
System.out.println(time);
}
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八、UTC时间与北京时间转换
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public static void main(String[] args) throws ParseException {
Date now = new Date();
Date utcDate = bj2UTC(now);
//utc时间
System.out.println(utcDate);
//北京时间
System.out.println(utc2BJ(utcDate));
DateTime dateTime = DateTime.now().withDayOfMonth( 1 ).withHourOfDay( 0 ).withMinuteOfHour( 0 ).withSecondOfMinute( 0 );
System.out.println(dateTime);
System.out.println(bj2UTC(dateTime.toDate()));
}
public static Date bj2UTC(Date date) {
if (date == null ) {
return null ;
}
LocalDateTime localDateTime = LocalDateTime.ofInstant(date.toInstant(), ZoneId.of( "-8" ));
return Date.from(localDateTime.atOffset(ZoneOffset.UTC).toInstant());
}
public static Date utc2BJ(Date date) {
if (date == null ) {
return null ;
}
LocalDateTime localDateTime = LocalDateTime.ofInstant(date.toInstant(), ZoneId.of( "+8" ));
return Date.from(localDateTime.atOffset(ZoneOffset.UTC).toInstant());
}
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北京时间=UTC+8
总结
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原文链接:https://juejin.cn/post/7022923059992461320