Java如何操纵LocalDate对象的值？

在下面的示例中，我们将学习如何操作LocalDate对象。有许多方法可用于更改LocalDate对象的值。例如，我们可以更改对象的年，月和日LocalDate。我们可以用类似的方法withYear()，withDayOfMonth()，plusYears()，minusMonths()，等所有这些方法都将返回一个新LocalDate的对象，原来LocalDate将保持不变。

让我们看下面的代码示例，以演示如何操纵LocalDate对象的值。

package org.nhooo.example.datetime;

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

public class LocalDateManipulation {
    public static void main(String[] args) {
        absoluteAttributeManipulations();
        relativeAttributeManipulations();
    }

    private static void relativeAttributeManipulations() {
        System.out.println("LocalDateManipulation.relativeAttributeManipulations");
        LocalDate date1 = LocalDate.of(2015, Month.AUGUST, 17);
        LocalDate date2 = date1.minusYears(70);
        LocalDate date3 = date2.plusMonths(10);
        LocalDate date4 = date3.minusDays(15);
        LocalDate date5 = date4.plusWeeks(52);
        LocalDate date6 = date5.minus(52, ChronoUnit.WEEKS);

        System.out.println("of(2015, Month.AUGUST, 17)        => " + date1);
        System.out.println("date1.minusYears(70)              => " + date2);
        System.out.println("date1.plusMonths(10)              => " + date3);
        System.out.println("date3.minusDays(15)               => " + date4);
        System.out.println("date4.plusWeeks(52)               => " + date5);
        System.out.println("date5.minus(52, ChronoUnit.WEEKS) => " + date6);

    }

    private static void absoluteAttributeManipulations() {
        System.out.println("LocalDateManipulation.absoluteAttributeManipulations");
        LocalDate date1 = LocalDate.of(2016, Month.JANUARY, 1);
        LocalDate date2 = date1.withYear(2010);
        LocalDate date3 = date2.withMonth(Month.DECEMBER.getValue());
        LocalDate date4 = date3.withDayOfMonth(15);
        LocalDate date5 = date4.with(ChronoField.DAY_OF_YEAR, 100);

        System.out.println("of(2016, Month.JANUARY, 1)                 => " + date1);
        System.out.println("date1.withYear(2010)                       => " + date2);
        System.out.println("date2.withMonth(Month.DECEMBER.getValue()) => " + date3);
        System.out.println("date3.withDayOfMonth(15)                   => " + date4);
        System.out.println("date4.with(ChronoField.DAY_OF_YEAR, 100)   => " + date5);
    }
}

此代码段的结果是：

LocalDateManipulation.absoluteAttributeManipulations
of(2016, Month.JANUARY, 1)                 => 2016-01-01
date1.withYear(2010)                       => 2010-01-01
date2.withMonth(Month.DECEMBER.getValue()) => 2010-12-01
date3.withDayOfMonth(15)                   => 2010-12-15
date4.with(ChronoField.DAY_OF_YEAR, 100)   => 2010-04-10

LocalDateManipulation.relativeAttributeManipulations
of(2015, Month.AUGUST, 17)        => 2015-08-17
date1.minusYears(70)              => 1945-08-17
date1.plusMonths(10)              => 1946-06-17
date3.minusDays(15)               => 1946-06-02
date4.plusWeeks(52)               => 1947-06-01
date5.minus(52, ChronoUnit.WEEKS) => 1946-06-02