LocalDate、LocalTime、LocalDateTime、DateTimeFormatter

使用 Instant 代替 Date，LocalDateTime 代替 Calendar， DateTimeFormatter 代替 SimpleDateFormat

参考：什么？你项目还在用 Date 表示时间？！

LocalDateTime 是线程安全的

获取当前此刻的时间

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LocalDateTime rightNow = LocalDateTime.now();
System.out.println( "当前时刻: " + rightNow);
System.out.println( "当前年份: " + rightNow.getYear());
System.out.println( "当前月份: " + rightNow.getMonth());
System.out.println( "当前日份: " + rightNow.getDayOfMonth());
System.out.println( "当前时: " + rightNow.getHour());
System.out.println( "当前分: " + rightNow.getMinute());
System.out.println( "当前秒: " + rightNow.getSecond());

//输出结果：
当前时刻: 2019-12-13T22:05:26.779当前年份: 2019
当前月份: DECEMBER
当前日份: 13
当前时：22
当前分: 5
当前秒：26

构造一个指定年、月、日的时间

比如，想构造：2019年10月12月12日9时21分32秒

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LocalDateTime date = LocalDateTime.of(2019, Month.DECEMBER, 12, 9, 21, 32);

修改日期

注意：返回值为修改后的值

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LocalDateTime rightNow = LocalDateTime.now();

//增加 2 个小时
rightNow = rightNow.plusHours(2);

//增加 2 天
rightNow = rightNow.plusDays(2);

//增加3个月
rightNow = rightNow.plusMonths(3); 

//减少2年
rightNow = rightNow.minusYears(2);

//直接修改年份到2008年
rightNow = rightNow.withYear(2008); 

//直接修改小时到13时
rightNow = rightNow.withHour(13);

格式化日期 format

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LocalDateTime rightNow = LocalDateTime.now();
String result1 = rightNow.format(DateTimeFormatter.ISO_DATE);
string result2 = rightNow.format(DateTimeFormatter.BASIC_ISO_DATE);
String result3 = rightNow.format(DateTimeFormatter.ofPattern("yyyy/MM/dd"));
String result3 = rightNow.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm"));
String result4 = rightNow.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));

System.out.println("格式化后的日期（基本样式一举例）: " + result1);
System.out.println("格式化后的日期(基本样式二举例): " + result2);
System.out.println("格式化后的日期(自定义样式举例）: " + result3);
System.out.println("格式化后的日期(自定义样式举例）: " + result4);

//输出结果
格式化后的日期（基本样式一举例）: 2020-07-10
格式化后的日期(基本样式二举例): 20200710
格式化后的日期(自定义样式举例）: 2020/07/10
格式化后的日期(自定义样式举例）: 2020-07-10 18:38
格式化后的日期(自定义样式举例）: 2020-07-10 18:38:30

时间反解析

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LocalDate localDate = LocalDate.parse("2023-05-16");

Date 与 LocalDate 间转换

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public static Date asDate(LocalDate localDate) {
  return Date.from(localDate.atStartOfDay().atZone(ZoneId.systemDefault()).toInstant());
}

public static Date asDate(LocalDateTime localDateTime) {
  return Date.from(localDateTime.atZone(ZoneId.systemDefault()).toInstant());
}

public static LocalDate asLocalDate(Date date) {
  return Instant.ofEpochMilli(date.getTime()).atZone(ZoneId.systemDefault()).toLocalDate();
}

public static LocalDateTime asLocalDateTime(Date date) {
  return Instant.ofEpochMilli(date.getTime()).atZone(ZoneId.systemDefault()).toLocalDateTime();
}

DateTimeFormatter

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DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
System.out.println(dateTimeFormatter.format(LocalDateTime.now()));  //2021-09-23 14:33

Instant

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// 获得当前时间 
Instant instant = Instant.now();
// 以ISO-8601输出 
System.out.println(instant);

//在现在的时间上加上5个小时4分钟:plus() 方法会产生一个新的实例
Instant instant1 = instant.plus(Duration.ofHours(5).plusMinutes(4));

//计算5天前的时间
instant.minus(5, ChronoUnit.DAYS); // Option 1　方法1 
instant.minus(Duration.ofDays(5)); // Option 2  方法2 
      
//计算两个Instant之间的分钟数 
long diffAsMinutes = instant.periodUntil(instant1, ChronoUnit.MINUTES); // 方法1 
long diffAsMinutes = ChronoUnit.MINUTES.between(instant, instant1); // 方法2

// 用compareTo方法比较
// instant1.compareTo(instant)=1
System.out.format("instant1.compareTo(instant)=%d.%n", instant1.compareTo(instant)); 
      
// 使用isAfter()和isBefore() 
// instant1.isAfter(instant)=true, instant1.isBefore(instant)=false
System.out.format("instant1.isAfter(instant)=%b, instant1.isBefore(instant)=%b.%n",  
instant1.isAfter(instant), instant1.isBefore(instant))

转Date

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//Timestamp转Date
Date timestampDate = new Date(timestamp.getTime());

//Calendar转Date
Date calendarDate = calendar.getTime();

//Instant转Date
Date instantDate = Date.from(instant);

//LocalDateTime转Date
Date localDateTimeDate = Date.from(localDateTime.atZone(ZoneId.systemDefault()).toInstant());

//ZonedDateTime转Date
Date zonedDateTimeDate = Date.from(zonedDateTime.toInstant());

//LocalDate转Date
Date localDateDate = Date.from(localDate.atStartOfDay(ZoneId.systemDefault()).toInstant());

转Instant

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//Date转Instant
Instant dateInstant = date.toInstant();

//Timestamp转Instant
Instant timestampInstant = timestamp.toInstant();

//Calendar转Instant
Instant calendarInstant = calendar.toInstant();

//LocalDateTime转Instant
Instant localDateTimeInstant = localDateTime.atZone(ZoneId.systemDefault()).toInstant();

//ZonedDateTime转Instant
Instant zonedDateTimeInstant = zonedDateTime.toInstant();

//LocalDate转Instant
Instant localDateInstant = localDate.atStartOfDay(ZoneId.systemDefault()).toInstant();

//TemporalAccessor 转 Instant
TemporalAccessor temporalAccessor = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss").parse("2003-11-19 11:20:20");
Instant instant = Instant.from(temporalAccessor);

转LocalDateTime

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//Date转LocalDateTime
LocalDateTime dateLocalDateTime = 	     LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault());

//Timestamp转LocalDateTime
LocalDateTime timestampLocalDateTime = timestamp.toLocalDateTime();

//Calendar转LocalDateTime
LocalDateTime calendarLocalDateTime = LocalDateTime.ofInstant(calendar.toInstant(), ZoneOffset.systemDefault());

//Instant转LocalDateTime
LocalDateTime instantLocalDateTime = LocalDateTime.ofInstant(instant, ZoneId.systemDefault());

//ZonedDateTime转LocalDateTime
LocalDateTime zonedDateTimeLocalDateTime = zonedDateTime.toLocalDateTime();

//LocalDate转LocalDateTime
LocalDateTime localDateLocalDateTime = localDate.atStartOfDay();

转Timestamp

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//Date转Timestamp
Timestamp dateTimestamp = new Timestamp(date.getTime());

//Calendar转Timestamp
Timestamp calendarTimestamp = new Timestamp(calendar.getTimeInMillis());

//Instant转Timestamp
Timestamp instantTimestamp = Timestamp.from(instant);

//LocalDateTime转Timestamp
Timestamp localDateTimeTimestamp = Timestamp.valueOf(localDateTime);

//ZonedDateTime转Timestamp
Timestamp zonedDateTimeTimestamp = Timestamp.from(zonedDateTime.toInstant());

//LocalDate转Timestamp
Timestamp localDateTimestamp = Timestamp.valueOf(localDate.atStartOfDay());

转Calendar

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//Date转Calendar
Calendar dateCalendar = Calendar.getInstance();
dateCalendar.setTime(date);

//Timestamp转Calendar
Calendar timestampCalendar = Calendar.getInstance();
timestampCalendar.setTimeInMillis(timestamp.getTime());

//Instant转Calendar
Calendar instantCalendar = GregorianCalendar.from(ZonedDateTime.ofInstant(instant, ZoneId.systemDefault()));

//LocalDateTime转Calendar
Calendar localDateTimeCalendar = GregorianCalendar.from(ZonedDateTime.of(localDateTime, ZoneId.systemDefault()));

//ZonedDateTime转Calendar
Calendar zonedDateTimeInstantCalendar = GregorianCalendar.from(zonedDateTime);

//LocalDate转Calendar
Calendar localDateCalendar = GregorianCalendar.from(localDate.atStartOfDay(ZoneId.systemDefault()));

转LocalDate

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//Date转LocalDate
LocalDate dateLocalDate = LocalDate.ofInstant(date.toInstant(), ZoneId.systemDefault());  //jdk11

LocalDate dateLocalDate = LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault()).toLocalDate();

//Timestamp转LocalDate
LocalDate timestampLocalDate = timestamp.toLocalDateTime().toLocalDate();

//Calendar转LocalDate
LocalDate calendarLocalDate = LocalDate.ofInstant(calendar.toInstant(), ZoneOffset.systemDefault());  //jdk11

LocalDate calendarLocalDate = LocalDateTime.ofInstant(calendar.toInstant(), ZoneOffset.systemDefault()).toLocalDate();

//Instant转LocalDate
LocalDate instantLocalDate = LocalDate.ofInstant(instant, ZoneId.systemDefault());  //jdk11

LocalDate instantLocalDate = LocalDateTime.ofInstant(instant, ZoneId.systemDefault()).toLocalDate();

//LocalDateTime转LocalDate
LocalDate localDateTimeLocalDate = localDateTime.toLocalDate();

//ZonedDateTime转LocalDate
LocalDate zonedDateTimeLocalDate = zonedDateTime.toLocalDate();

SimpleDateFormat

线程不安全

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//线程安全
public static ThreadLocal<SimpleDateFormat> date_sdf = new ThreadLocal<SimpleDateFormat>() {
    @Override
    protected SimpleDateFormat initialValue() {
        return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    }
};

//当前时间
date_sdf.get().format(new Date())

代码片段

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// 获取指定年份 1 月 1 号日期，示例 2023-01-01
LocalDate startDate = LocalDate.of(year, 1, 1);

// 获取指定年份指定月份最后一天日期，示例 2023-12-31
LocalDate endDate = YearMonth.of(year, 12).atEndOfMonth();

// 获取当月开始日期，示例：2023-11-01 00:00:00
public static DateTime oneMonthAgo() {
    return DateUtil.beginOfMonth(DateUtil.date());
}

// 当前日期 7天前的日期
public static DateTime sevenDaysAgo() {
    return DateUtil.beginOfDay(DateUtil.offsetDay(DateUtil.date(), -7));
}

// 获取指定日期加若干天后的日期
public static DateTime getDateTimeOffsetDays(Date date, int days) {
    return DateUtil.offsetDay(date, days);
}

// 根据年份，获取随机日期，要求小于当前日期
public static List<LocalDate> getDatesInYear(int year) {
  List<LocalDate> dates = new ArrayList<>();
  LocalDate startDate = LocalDate.of(year, 1, 1);
  LocalDate endDate = YearMonth.of(year, 12).atEndOfMonth();

  if (year == LocalDate.now().getYear()) {
    endDate = LocalDate.now();
  }

  for (LocalDate date = startDate; date.isBefore(endDate); date = date.plusDays(1)) {
    dates.add(date);
  }

  return dates;
}

获取 2 个时间之间随机的时间

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// 获取 2 个时间之间随机时间
public static LocalTime getRandomTime(LocalTime startTime, LocalTime endTime) {
  long startSeconds = startTime.toSecondOfDay();
  long endSeconds = endTime.toSecondOfDay();
  long randomSeconds = startSeconds + (long)(Math.random() * (endSeconds - startSeconds));
  return LocalTime.ofSecondOfDay(randomSeconds);
}

根据年份，获取随机日期，要求小于当前日期

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// 根据年份，获取随机日期，小于当前日期
  public static List<LocalDate> getDatesInYear(int year) {
    List<LocalDate> dates = new ArrayList<>();
    LocalDate startDate = LocalDate.of(year, 1, 1);
    LocalDate endDate = YearMonth.of(year, 12).atEndOfMonth();

    if (year == LocalDate.now().getYear()) {
      endDate = LocalDate.now();
    }

    for (LocalDate date = startDate; date.isBefore(endDate); date = date.plusDays(1)) {
      dates.add(date);
    }

    return dates;
  }