Java 8: LocalDate, LocalTime, LocalDateTime handle date and time

In JDK8, three new classes have been added to deal with time.

LocalDate specializes in processing dates, LocalTime specializes in processing time, LocalDateTime includes date and time, and provides ready-made methods for many complex problems, such as obtaining the first Monday in December 2017.

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);
    }
}

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());
    }
 
}