java8 新时间API用法实例(LocalDate、LocalTime、LocalDateTime)

java8 新时间API用法实例(LocalDate、LocalTime、LocalDateTime)

java8之前，Date类都是可变的。在多线程环境下使用它，开发人员需考虑Date对象的线程安全。Java8新的处理时间的 API提供了线程安全的不可变类，开发人员不需要再考虑并发所带来的安全问题。

下面是一些新API的经常用到的方法，当然还有很多也常用，这里就不一一列出，有兴趣的可以看看源码，一下代码如有不正确的还望不吝赐教。

下面的例子主要从以下几个类演示用法：
LocalDate、LocalTime、LocalDateTime、DateTimeFormatter

个人体验新的时间API类比以前好用多了，谁用谁知道，尤其在时间的计算方面，灵活、简单、方便。

---

格式器说明
 * All letters 'A' to 'Z' and 'a' to 'z' are reserved as pattern letters. The following pattern letters are defined:
 * 

 * Symbol  Meaning                     Presentation      Examples
 * ------  -------                     ------------      -------
 * G       era                         text              AD; Anno Domini; A
 * u       year                        year              2004; 04
 * y       year-of-era                 year              2004; 04
 * D       day-of-year                 number            189
 * M/L     month-of-year               number/text       7; 07; Jul; July; J
 * d       day-of-month                number            10
 * 

 * Q/q     quarter-of-year             number/text       3; 03; Q3; 3rd quarter
 * Y       week-based-year             year              1996; 96
 * w       week-of-week-based-year     number            27
 * W       week-of-month               number            4
 * E       day-of-week                 text              Tue; Tuesday; T
 * e/c     localized day-of-week       number/text       2; 02; Tue; Tuesday; T
 * F       week-of-month               number            3
 * 

 * a       am-pm-of-day                text              PM
 * h       clock-hour-of-am-pm (1-12)  number            12
 * K       hour-of-am-pm (0-11)        number            0
 * k       clock-hour-of-am-pm (1-24)  number            0
 * 

 * H       hour-of-day (0-23)          number            0
 * m       minute-of-hour              number            30
 * s       second-of-minute            number            55
 * S       fraction-of-second          fraction          978
 * A       milli-of-day                number            1234
 * n       nano-of-second              number            987654321
 * N       nano-of-day                 number            1234000000
 * 

 * V       time-zone ID                zone-id           America/Los_Angeles; Z; -08:30
 * z       time-zone name              zone-name         Pacific Standard Time; PST
 * O       localized zone-offset       offset-O          GMT+8; GMT+08:00; UTC-08:00;
 * X       zone-offset 'Z' for zero    offset-X          Z; -08; -0830; -08:30; -083015; -08:30:15;
 * x       zone-offset                 offset-x          +0000; -08; -0830; -08:30; -083015; -08:30:15;
 * Z       zone-offset                 offset-Z          +0000; -0800; -08:00;
 * 

 * p       pad next                    pad modifier      1
 * 

 * '       escape for text             delimiter
 * ''      single quote                literal           '
 * [       optional section start
 * ]       optional section end
 * #       reserved for future use
 * {       reserved for future use
 * }       reserved for future use
 */

    import java.time.LocalDate;
    import java.time.LocalDateTime;
    import java.time.LocalTime;
    import java.time.format.DateTimeFormatter;

    /**
     * Created by LHL on 2016/11/22.
    */
    public class Demo01 {
        public static void main(String[] args) {

        LocalDateTime localDateTime = LocalDateTime.now();
        System.out.println("系统当前日期+时间:" + localDateTime);
        LocalDate localDate = LocalDate.now();
        System.out.println("系统当期日期：" + localDate);
        LocalTime localTime = LocalTime.now();
        System.out.println("系统当前时间：" + localTime);
        System.out.println("系统当前时间,去除毫秒：" + localTime.withNano(0));//0 为去除毫秒

        System.out.println("指定年、月、日、时、分、秒：" + LocalDateTime.of(2016, 11, 23, 9, 07, 59));//返回一个指定年、月、日、时、分、秒的时间，不可变
        System.out.println("指定年数的时间：" + localDateTime.withDayOfYear(1));//返回一个指定“一年中的天数,the day-of-year  ”的时间，不可变
        System.out.println("指定天数的时间：" + localDateTime.withDayOfMonth(1));//返回一个指定“一月中的天数,day-of-month ”的时间，不可变
        System.out.println("指定小时数的时间：" + localTime.withHour(1));//返回一个指定“一天中的小时数,the hour-of-day ”的时间，不可变
        System.out.println("指定分钟数的时间：" + localTime.withMinute(1));//返回一个指定“一小时的分钟数,the minute-of-hour ”的时间，不可变
        System.out.println("指定秒数的时间：" + localTime.withSecond(1));//返回一个指定“一分钟的秒数,the second-of-minute ”的时间，不可变
        System.out.println("the hour-of-day, from 0 to 23：" + localTime.getHour());//取得一天中的小时数
        System.out.println("minute-of-hour, from 0 to 59:" + localTime.getMinute());//取得一小时中的分钟数
        System.out.println("the second-of-minute, from 0 to 59:" + localTime.getSecond());//取的一分钟的秒数
        System.out.println("the nano-of-second, from 0 to 999,999,999:" + localTime.getNano());//取得一秒钟的纳秒数

        //日期运算
        System.out.println("系统当前时间减去1年：" + (localDate.minusYears(1)));
        //看看闰年和平年的区别
        LocalDateTime localDateTime1 = LocalDateTime.of(2016, 02, 29, 00, 00, 00);
        System.out.println("闰年减去一年：" + localDateTime1.minusYears(1));//减去一年后是平年，注意结果
        System.out.println("系统当前时间减去1天：" + (localDate.minusDays(1)));
        System.out.println("系统当前时间减去23天：" + (localDate.minusDays(23)));
        System.out.println("系统当前时间加上1年：" + (localDate.plusYears(1)));
        System.out.println("系统当前时间加上1天：" + (localDate.plusDays(1)));
        System.out.println("系统当前时间加上1分钟：" + (localDateTime.plusMinutes(1)));
        System.out.println("系统当前时间加上1纳秒：" + (localDateTime.plusNanos(1)));
        System.out.println("系统当前时间加上1周：" + (localDateTime.plusWeeks(1)));
        System.out.println("localDateTime 转 localDate:" + localDateTime.toLocalDate());
        System.out.println("localDateTime 转 localTime:" + localDateTime.toLocalTime());
        //格式器
        DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyyMMdd HH:mm:ss");
        System.out.println(LocalDateTime.parse("20111123 00:00:00", dateTimeFormatter));
        System.out.println(LocalDateTime.MIN);//支持的最小时间
        System.out.println(LocalDateTime.MAX);//支持的最大时间
    }
}