java8日期类LocalDate,LocalTime和LocalDateTime的基本操作

　　至于为什么使用java8日期类以及Date的缺点等这里不做多解释, 直接上代码, 代码中都是日常项目中最可能用到的一些基本操作

　1.LocalDate类

package demo.java.jiangkd.java8.localdate;

import java.time.DayOfWeek;
import java.time.LocalDate;
import java.time.Month;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoField;
import java.time.temporal.ChronoUnit;

import org.junit.Test;

import lombok.extern.slf4j.Slf4j;

/**
 * LocalDate

 * LocalDate只会获取年月日
 * 
 * @author jiangkd
 * @date 2020/06/05
 */
@Slf4j
public class LocalDateDemo {

    /**
     * 创建LocalDate
     */
    @Test
    public void createLocalDateTest() {
        // 获取当前年月日
        LocalDate now = LocalDate.now();
        log("now", now); // 打印格式: yyyy-MM-dd, 例如: 2020-06-05
        // 构造指定的年月日
        now = LocalDate.of(2020, Month.JUNE, 5);
        log("now", now); // 2020-06-05
    }

    /**
     * 获取年、月、日、星期几 的几种方式
     */
    @Test
    public void getDateTest() {
        //
        LocalDate now = LocalDate.now();
        // 年
        int year = now.getYear();
        log("year", year);
        year = now.get(ChronoField.YEAR);
        log("year", year); // 2020
        // 月 , 1-12表示相应的月份
        Month month = now.getMonth();
        log("month", month);
        log("month", month.getValue());
        int monthValue = now.getMonthValue();
        log("month", monthValue);
        int month2 = now.get(ChronoField.MONTH_OF_YEAR);
        log("month2", month2); // 6
        // 日
        int dayOfMonth = now.getDayOfMonth();
        log("dayOfMonth", dayOfMonth);
        int day = now.get(ChronoField.DAY_OF_MONTH);
        log("day", day); // 5
        // 星期, 1-7对应星期一星期日
        DayOfWeek dayOfWeek = now.getDayOfWeek();
        log("dayOfWeek", dayOfWeek);
        log("dayOfWeek", dayOfWeek.getValue());
        int week = now.get(ChronoField.DAY_OF_WEEK);
        log("week", week); // 5
    }

    /**
     * 对日期进行加减操作
     */
    @Test
    public void plusOrMinusTest() {
        //
        LocalDate now = LocalDate.now();
        log("now", now); // 2020-06-05
        // 对年 + 1
        now = now.plusYears(1);
        log("now", now); // 2021-06-05
        // 对月+2
        now = now.plusMonths(2);
        log("now", now); // 2021-08-05
        // 对月在加5, 等于13, 但是只有12个月, 会对年进行加1
        now = now.plusMonths(5);
        log("now", now); // 2022-01-05
        // 重置now对象, 6月30天, 测试日加上30天
        now = LocalDate.now();
        log("now", now); // 2020-06-05
        //
        now = now.plusDays(30);
        log("now", now); // 2020-07-05
        // 对日期的修改还可以使用下面的方法
        now = LocalDate.now(); //
        log("now", now); // 2020-06-05
        now = now.plus(30, ChronoUnit.DAYS).minus(2, ChronoUnit.MONTHS);
        log("now", now); // 2020-05-05

        // 相应的减操作 now.minus和plus类似, 不做赘述
    }

    /**
     * 日期格式化
     */
    @Test
    public void localDateFormatterTest() {
        //
        LocalDate now = LocalDate.now();
        log("now", now); // 2020-06-05
        //
        String format = now.format(DateTimeFormatter.ofPattern("yyyy/MM/dd"));
        log("format", format); // 2020/06/05
    }

    private void log(String info, Object obj) {
        log.info("{} -> {}", info, obj);
    }
}

 　　2.LocalTime类

package demo.java.jiangkd.java8.localdate;

import java.time.LocalTime;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoField;

import org.junit.Test;

import lombok.extern.slf4j.Slf4j;

@Slf4j
public class LocalTimeDemo {

    /**
     * 创建LocalDateTime
     */
    @Test
    public void createLocalTimeTest() {
        //
        LocalTime now = LocalTime.now();
        log("now", now); // 09:09:18.450
        // 构建LocalTime, 参数分别是 时,分,秒
        now = LocalTime.of(9, 10, 30);
        log("now", now); // 09:10:30
    }

    /**
     * 获取时分秒
     */
    @Test
    public void getTimeTest() {
        //
        LocalTime now = LocalTime.now();
        // 时
        int hour = now.getHour();
        log("hour", hour);
        hour = now.get(ChronoField.HOUR_OF_DAY);
        log("hour", hour);
        // 分
        int minute = now.getMinute();
        log("minute", minute);
        minute = now.get(ChronoField.MINUTE_OF_HOUR);
        log("minute", minute);
        // 秒
        int second = now.getSecond();
        log("second", second);
        second = now.get(ChronoField.SECOND_OF_MINUTE);
        log("second", second);
    }

    @Test
    public void localTimeFormatterTest() {
        //
        LocalTime now = LocalTime.now();
        log("now", now);
        //
        String format = now.format(DateTimeFormatter.ofPattern("HH:mm:ss"));
        log("format", format); // 09-58-10
        format = now.format(DateTimeFormatter.ofPattern("HH:mm:ss,SSS"));
        log("format", format); // 09-58-10,912
    }

    private void log(String info, Object obj) {
        log.info("{} -> {}", info, obj);
    }
}

　　3.LocalDateTime类

package demo.java.jiangkd.java8.localdate;

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

import org.junit.Test;

import lombok.extern.slf4j.Slf4j;

/**
 * LocalDateTime,获取年月日时分秒，等于LocalDate+LocalTime
 * 
 * @author jiangkd
 * @date 2020/06/05
 */
@Slf4j
public class LocalDateTimeDemo {

    /**
     * 创建LocalDateTime
     */
    @Test
    public void createLocalDateTimeTest() {
        //
        LocalDateTime now = LocalDateTime.now();
        log("now", now); // now -> 2020-06-05T09:28:39.095
        now = LocalDateTime.of(LocalDate.now(), LocalTime.now());
        log("now", now); // now -> 2020-06-05T09:28:39.112
    }

    /**
     * 获取LocalDate和LocalTime
     */
    @Test
    public void getLocalDateOrTimeTest() {
        //
        LocalDateTime now = LocalDateTime.now();
        // 获取LocalDate
        LocalDate localDate = now.toLocalDate();
        log("localDate", localDate); // 2020-06-05
        // 获取LocalTime
        LocalTime localTime = now.toLocalTime();
        log("localTime", localTime); // 09:30:53.802
    }

    /**
     * 格式化
     */
    @Test
    public void localDateTimeFormatterTest() {
        //
        LocalDateTime now = LocalDateTime.now();
        log("now", now); // 2020-06-05T10:01:05.556
        //
        String format = now.format(DateTimeFormatter.ofPattern("yyyy/MM/dd HH-mm-ss"));
        log("format", format); // 2020/06/05 10-01-05
    }

    private void log(String info, Object obj) {
        log.info("{} -> {}", info, obj);
    }
}