Period และการคำนวณวันที่

ปริมาณเวลาตามวันที่

การเพิ่มวัน

import java.time.LocalDate;

public class Main {
    public static void main(String[] args) {
        LocalDate start = LocalDate.of(2026, 5, 30);
        System.out.println(start.plusDays(10));
    }
}

การเพิ่มเดือนและปี

import java.time.LocalDate;

public class Main {
    public static void main(String[] args) {
        LocalDate start = LocalDate.of(2026, 1, 31);
        System.out.println(start.plusMonths(1));
        System.out.println(start.plusYears(2));
    }
}

การลบวันที่

import java.time.LocalDate;

public class Main {
    public static void main(String[] args) {
        LocalDate date = LocalDate.of(2026, 5, 30);
        System.out.println(date.minusWeeks(2));
    }
}

การสร้าง Period

import java.time.LocalDate;
import java.time.Period;

public class Main {
    public static void main(String[] args) {
        Period p = Period.of(1, 2, 3);
        LocalDate date = LocalDate.of(2026, 1, 1);
        System.out.println(date.plus(p));
    }
}

Period ระหว่างวันที่

import java.time.LocalDate;
import java.time.Period;

public class Main {
    public static void main(String[] args) {
        LocalDate from = LocalDate.of(2020, 1, 15);
        LocalDate to = LocalDate.of(2026, 5, 30);
        Period p = Period.between(from, to);
        System.out.println(p.getYears() + "y " + p.getMonths() + "m " + p.getDays() + "d");
    }
}

การคำนวณอายุ

import java.time.LocalDate;
import java.time.Period;

public class Main {
    public static void main(String[] args) {
        LocalDate birth = LocalDate.of(2000, 6, 15);
        LocalDate today = LocalDate.of(2026, 5, 30);
        int age = Period.between(birth, today).getYears();
        System.out.println(age);
    }
}

การนับจำนวนวันทั้งหมด

import java.time.LocalDate;
import java.time.temporal.ChronoUnit;

public class Main {
    public static void main(String[] args) {
        LocalDate from = LocalDate.of(2026, 1, 1);
        LocalDate to = LocalDate.of(2026, 12, 31);
        long days = ChronoUnit.DAYS.between(from, to);
        System.out.println(days);
    }
}

ความยืดหยุ่นของ ChronoUnit

import java.time.LocalDate;
import java.time.temporal.ChronoUnit;

public class Main {
    public static void main(String[] args) {
        LocalDate from = LocalDate.of(2026, 1, 1);
        LocalDate to = LocalDate.of(2026, 12, 31);
        System.out.println(ChronoUnit.WEEKS.between(from, to));
        System.out.println(ChronoUnit.MONTHS.between(from, to));
    }
}

การค้นหาวันในสัปดาห์ถัดไป

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

public class Main {
    public static void main(String[] args) {
        LocalDate date = LocalDate.of(2026, 5, 30);
        System.out.println(date.with(TemporalAdjusters.firstDayOfNextMonth()));
    }
}

Period กับ ChronoUnit

ตรวจสอบความเข้าใจ

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