获取当年、当月的开始结束日期

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.temporal.TemporalAdjusters;

/**
 * 根据当前时间获取特定的日期或时间
 * 主要思路是使用 TemporalAdjusters 工具类获取当前特定的日期，然后再通过 LocalDateTime.of 将特定的日期与特定的时间组合成最终的 LocalDateTime。
 */
class Scratch {
    public static void main(String[] args) {

        LocalDate nowDate = LocalDate.now();

        LocalDate firstDayOfYear = nowDate.with(TemporalAdjusters.firstDayOfYear());
        LocalDate lastDayOfYear = nowDate.with(TemporalAdjusters.lastDayOfYear());
        LocalDateTime firstDateOfYear = LocalDateTime.of(firstDayOfYear, LocalTime.MIN);
        LocalDateTime lastDateOfYear = LocalDateTime.of(lastDayOfYear, LocalTime.MAX);

        LocalDate firstDayOfMonth = nowDate.with(TemporalAdjusters.firstDayOfMonth());
        LocalDate lastDayOfMonth = nowDate.with(TemporalAdjusters.lastDayOfMonth());
        LocalDateTime firstDateOfMonth = LocalDateTime.of(firstDayOfMonth, LocalTime.MIN);
        LocalDateTime lastDateOfMonth = LocalDateTime.of(lastDayOfMonth, LocalTime.MAX);

        LocalDateTime fistDateOfDay = LocalDateTime.of(nowDate, LocalTime.MIN);
        LocalDateTime lastDateOfDay = LocalDateTime.of(nowDate, LocalTime.MAX);


        System.out.println("当前时间：" + LocalDateTime.now());

        System.out.println("今年第一天：" + firstDateOfYear);
        System.out.println("今天最后一天：" + lastDateOfYear);

        System.out.println("当月第一天：" + firstDateOfMonth);
        System.out.println("当月最后一天：" + lastDateOfMonth);

        System.out.println("当天开始时间：" + fistDateOfDay);
        System.out.println("当天结束时间：" + lastDateOfDay);
//        print：
//        当前时间：2020-04-17T10:10:40.443
//        今年第一天：2020-01-01T00:00
//        今天最后一天：2020-12-31T23:59:59.999999999
//        当月第一天：2020-04-01T00:00
//        当月最后一天：2020-04-30T23:59:59.999999999
//        当天开始时间：2020-04-17T00:00
//        当天结束时间：2020-04-17T23:59:59.999999999

    }
}