java - 在 LocalDate 对象上使用 equals 和 ==

Question

我有以下代码:

LocalDate one = LocalDate.of(2016, 1, 1);
LocalDate two = LocalDate.of(2016, 1, 1);
System.out.println(one.equals(two)); // true since contents are same
System.out.println(one == two); // false since references are diff
LocalDate newone = one.with(TemporalAdjusters.nextOrSame(DayOfWeek.FRIDAY));
System.out.println(newone.equals(one));// true since contents are still same
System.out.println(newone == one); //-4- why true here 

问题是为什么在 4 时它给出 true，因为 LocalDate 对象是不可变的，所以用 TemporalAdjuster 改变一个对象会给出一个新的 LocalDate 对象。如果newone和one的内容不一样

newone == one returns false

请更新此行为。谢谢

Answer 1

看一下TemporalAdjusters.nextOrSame的代码:

public static TemporalAdjuster nextOrSame(DayOfWeek dayOfWeek) {
    int dowValue = dayOfWeek.getValue();
    return (temporal) -> {
        int calDow = temporal.get(DAY_OF_WEEK);
        if (calDow == dowValue) {
            return temporal;  // <-- returns the original object!
        }
        int daysDiff = calDow - dowValue;
        return temporal.plus(daysDiff >= 0 ? 7 - daysDiff : -daysDiff, DAYS);
    };
}

来自documentation (强调我的):

Returns the next-or-same day-of-week adjuster, which adjusts the date to the first occurrence of the specified day-of-week after the date being adjusted unless it is already on that day in which case the same object is returned.

因此，如果不需要调整(因为 2016 年 1 月 1 日是星期五)，则返回相同对象。