Java 8: LocalDate, LocalTime, LocalDateTime manejan fecha y hora

En JDK8, se han agregado tres nuevas clases para lidiar con el tiempo.

LocalDate se especializa en procesar fechas, LocalTime se especializa en tiempo de procesamiento, LocalDateTime incluye fecha y hora, y proporciona métodos listos para usar para muchos problemas complejos, como obtener el primer lunes de diciembre de 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());
    }
 
}