Java中常用时间的一些相关方法

2024-04-02 19:55

短信预约 -IT技能 免费直播动态提醒

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


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);
}

获取当前时间可以使用Date LocalDatetime Calendar Datetime

二、获取当月第n天


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));
}

三、格式化为字符串


```
//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);
```

四、加减时间（单位可以是秒，小时等）


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));

    
    //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));
}

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


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());
}

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


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());
}

七、求两个时间间隔


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);
}

八、UTC时间与北京时间转换


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());
}

北京时间=UTC+8