比较方法违反了Java 7中的一般合同 [英] Comparison Method violates its general contract in Java 7

问题描述

我在Java 7中编译了一些Java代码，然后运行它后，得到了比较方法违反了它的一般合同。

I am getting a "Comparison Method violates its general contract" after compiling some Java code in Java 7, and then running it.

我读过比较方法违反了其总合同！仅限Java 7，并意识到我的代码在以前版本的Java中被忽略了。但是，我无法弄清楚我的代码有什么问题。 Collections.sort（）生成错误。

I have read Comparison method violates its general contract! Java 7 only and realize that there is something wrong with my code that was ignored in previous versions of Java. However I cannot work out what is wrong with my code. The Collections.sort() generates the error.

我的代码是：

   public Comparator sortBySmoothDays() {
    Comparator c = new Comparator() {
        public int compare(Object arg0, Object arg1) {
            Date date0 = ((PosObject)arg0).getDate();
            Date date1 = ((PosObject)arg1).getDate();

            double d1 = MyUtils.calcSmoothDays(date0, new Date());
            double d2 = MyUtils.calcSmoothDays(date1, new Date());
            if (d1 >= d2) {
                return 1;
            }
            else {
                return -1;
            }   
        }
    };
    return c;
}


Comparator c = ComparatorUtils.getInstance().sortBySmoothDays();
Collections.sort(posList, c);

任何人都可以提供帮助吗？谢谢！

Can anyone help? Thank you!

推荐答案

如果值相等，比较器必须返回0。在当前的实现中，如果它们相等则返回1。正确比较 double 值的最简单方法是调用 Double.compare ：

A comparator must return 0 if the values are equal. In your current implementation, you return 1 if they are equal. The easiest way to compare your double values correctly is to call Double.compare:

double d1 = MyUtils.calcSmoothDays(date0, new Date());
double d2 = MyUtils.calcSmoothDays(date1, new Date());

return Double.compare(d1, d2);

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