Java 8： LocalDate、LocalTime 、LocalDateTime 处理日期时间

阳光穿透心脏的1/2处 2024-04-19 08:35 80阅读 0赞

JDK8中，新增了三个类，用以处理时间。

LocalDate专门处理日期，LocalTime专门处理时间，LocalDateTime包含了日期和时间，而且对于很多复杂的问题，都提供了现成的方法，比如：获取2017年12月的第一个周一等。

package test;
     
    import java.time.DayOfWeek;
    import java.time.LocalDate;
    import java.time.LocalDateTime;
    import java.time.LocalTime;
    import java.time.temporal.TemporalAdjusters;
    import java.util.Calendar;
     
    /**
     * Created by lightClouds917
     * Date 2017/11/6
     * Description:Java8中处理时间和日期的类
     *
     SQL  -> Java
     --------------------------
     date -> LocalDate
     time -> LocalTime
     timestamp -> LocalDateTime
     */
    public class DateTest2 {
        public static void main(String[] args){
            test1();
            test2();
     
            Calendar calendar = Calendar.getInstance();
            System.out.println(calendar.getTime());
        }
     
        /**
         * 处理日期 LocalDate
         */
        public static void test1(){
            //获取当前日期   2017-11-06
            LocalDate today = LocalDate.now();
            System.out.println(today);
     
            //构造日期   2017-10-08
            LocalDate today2 = LocalDate.of(2017,10,8);
            System.out.println(today2);
     
            //构造日期   2017-02-22    字符串严格按照yyyy-MM-dd
            LocalDate today3 = LocalDate.parse("2017-02-22");
            System.out.println(today3);
     
            //本月第一天  2017-11-01
            LocalDate firstDayOfMonth = today.with(TemporalAdjusters.firstDayOfMonth());
            System.out.println(firstDayOfMonth);
            //本月第二天  2017-11-02   第n天
            LocalDate secondDayOfMonth = today.withDayOfMonth(2);
            System.out.println(secondDayOfMonth);
     
            //本月最后一天 2017-02-28  方便解决任何年份的二月份多少天
            LocalDate lastDayOfMonth = today3.with(TemporalAdjusters.lastDayOfMonth());
            System.out.println(lastDayOfMonth);
     
     
            //获取2017年12月的第一个周一   2017-12-04
            LocalDate firstDayOf201712 = LocalDate.parse("2017-12-01").with(TemporalAdjusters.firstInMonth(DayOfWeek.MONDAY));
            System.out.println(firstDayOf201712);
     
        }
     
        /**
         * 处理时间  LocalTime
         */
        public static void test2(){
            //获取当前时间  含有毫秒值  17:18:41.571
            LocalTime now = LocalTime.now();
            System.out.println(now);
     
            //获取当前时间   去掉毫秒值   17:45:41
            LocalTime now1 = LocalTime.now().withNano(0);
            System.out.println(now1);
            //00:46:46.651  提供了把时分秒都设为0的方法
            LocalTime now2 = LocalTime.now().withHour(0);
            System.out.println(now2);
     
            //构造时间  00:20:55
            LocalTime time1 = LocalTime.of(0,20,55);
            System.out.println(time1);
            //构造时间  05:43:22
            LocalTime time2 = LocalTime.parse("05:43:22");
            System.out.println(time2);
     
     
            //标准时间 2017-11-06T17:53:15.930
            LocalDateTime lt = LocalDateTime.now();
            System.out.println(lt);
        }
    }

及：

public class TimeTest {
     
        @Test
        public void testTime() {
            LocalDateTime time = LocalDateTime.now();
     
            System.out.println(time.toString()); //字符串表示
            System.out.println(time.toLocalTime()); //获取时间(LocalTime)
            System.out.println(time.toLocalDate()); //获取日期(LocalDate)
            System.out.println(time.getDayOfMonth()); //获取当前时间月份的第几天
            System.out.println(time.getDayOfWeek());  //获取当前周的第几天
            System.out.println(time.getDayOfYear());  //获取当前时间在该年属于第几天
            System.out.println(time.getHour());
            System.out.println(time.getMinute());
            System.out.println(time.getMonthValue());
            System.out.println(time.getMonth());
            System.out.println("-----------------------------------");
            //格式化输出
            DateTimeFormatter formatter = DateTimeFormatter.ofPattern("YYYY/MM/dd HH:mm:ss");
            System.out.println(time.format(formatter));
            //构造时间
            LocalDateTime startTime = LocalDateTime.of(2018, 1, 1, 20, 31, 20);
            LocalDateTime endTime = LocalDateTime.of(2018, 1, 3, 20, 31, 20);
            //比较时间
            System.out.println(time.isAfter(startTime));
            System.out.println(time.isBefore(endTime));
     
            //时间运算，相加相减
            System.out.println(time.plusYears(2)); //加2年
            System.out.println(time.plusDays(2)); //加两天
            System.out.println(time.minusYears(2)); //减两年
            System.out.println(time.minusDays(2)); //减两天
     
            //获取毫秒数(使用Instant)
            System.out.println(time.atZone(ZoneId.systemDefault()).toInstant().toEpochMilli());
            //获取秒数(使用Instant)
            System.out.println(time.atZone(ZoneId.systemDefault()).toInstant().getEpochSecond());
        }
     
    }