java8全新的日期和时间API

LocalDate、LocalTime、LocalDateTime是java8对日期、时间提供的新接口。实际使用中，计算日期就用LocalDate,计算日期加时刻用LocalDateTime，如果只有时刻就是LocalTime

LocalDate

只会获取年月日
创建LocalDate

//获取当前年月日
LocalDate localDate = LocalDate.now();
//构造指定的年月日
LocalDate localDate1 = LocalDate.of(2019, 9, 10);
//获取年、月、日、星期几
int year = localDate.getYear();
int year1 = localDate.get(ChronoField.YEAR);
Month month = localDate.getMonth();
int month1 = localDate.get(ChronoField.MONTH_OF_YEAR);
int day = localDate.getDayOfMonth();
int day1 = localDate.get(ChronoField.DAY_OF_MONTH);
DayOfWeek dayOfWeek = localDate.getDayOfWeek();
int dayOfWeek1 = localDate.get(ChronoField.DAY_OF_WEEK);

LocalTime

只会获取几点几分几秒

//创建LocalTime
LocalTime localTime = LocalTime.of(13, 51, 10);
LocalTime localTime1 = LocalTime.now();
//获取时分秒
//获取小时
int hour = localTime.getHour();
int hour1 = localTime.get(ChronoField.HOUR_OF_DAY);
//获取分
int minute = localTime.getMinute();
int minute1 = localTime.get(ChronoField.MINUTE_OF_HOUR);
//获取秒
int second = localTime.getSecond();
int second1 = localTime.get(ChronoField.SECOND_OF_MINUTE);

LocalDateTime

获取年月日时分秒，等于LocalDate+LocalTime

//创建LocalDateTime
LocalDateTime localDateTime = LocalDateTime.now();
LocalDateTime localDateTime1 = LocalDateTime.of(2019, Month.SEPTEMBER, 10, 14, 46, 56);
LocalDateTime localDateTime2 = LocalDateTime.of(localDate, localTime);
LocalDateTime localDateTime3 = localDate.atTime(localTime);
LocalDateTime localDateTime4 = localTime.atDate(localDate);
//获取LocalDate
LocalDate localDate2 = localDateTime.toLocalDate();
//获取LocalTime
LocalTime localTime2 = localDateTime.toLocalTime();

区别

Date如果不格式化，打印出的日期可读性差
Tue Sep 10 09:34:04 CST 2019
使用SimpleDateFormat对时间进行格式化，但SimpleDateFormat是线程不安全的。

遇到的问题

在使用fastJson中对Date时间输出时会把时间字段转换为时间戳,其他类型的时间不会转换

package org.example.kafka.message.enties;

import com.alibaba.fastjson.JSON;

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.util.Date;

public class DateTest {
    public static void main(String[] args) {
        Message message = new Message();
        message.setLocalDate(LocalDate.now());
        message.setTime(new Date());
        message.setName("date");
        message.setLocalDateTime(LocalDateTime.now());
        message.setLocalTime(LocalTime.now());
        System.out.println(JSON.toJSONString(message));
        //打印输出，把time转化为时间戳了
        //{"localDate":"2021-07-14","localDateTime":"2021-07-14T17:13:06.219",
        // "localTime":"17:13:06.219","name":"date","time":1626253986219}
    }

    static class Message {
        private String name;
        private Date time;
        private LocalDate localDate;
        private LocalDateTime localDateTime;
        private LocalTime localTime;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public Date getTime() {
            return time;
        }

        public void setTime(Date time) {
            this.time = time;
        }

        public LocalDate getLocalDate() {
            return localDate;
        }

        public void setLocalDate(LocalDate localDate) {
            this.localDate = localDate;
        }

        public LocalDateTime getLocalDateTime() {
            return localDateTime;
        }

        public void setLocalDateTime(LocalDateTime localDateTime) {
            this.localDateTime = localDateTime;
        }

        public LocalTime getLocalTime() {
            return localTime;
        }

        public void setLocalTime(LocalTime localTime) {
            this.localTime = localTime;
        }
    }
}