如何排序数组或ArrayList< Point> ASC先用x然后再用y？ [英] How to sort an array or ArrayList<Point> ASC first by x and then by y?

问题描述

我只想使用Collections.sort或Arrays.sort按x先排序一个点列表（类Point），然后再按y。

I just want to use Collections.sort or Arrays.sort to sort a list of points (class Point) by x first and then by y.

一个类Ponto实现Comparable像这样：

I have a class Ponto that implements Comparable like this:

public int compareTo(Ponto obj) {
        Ponto tmp = obj;
        if (this.x < tmp.x) {
            return -1;
        } else if (this.x > tmp.x) {
            return 1;
        }
        return 0;
    }

但现在我想在x之后再按y排序。

but now I want to sort by y too after x.

我如何通过修改上面的代码？或者是一个更好和干净的方式做到这一点？
我也使用把这段代码传递给C ++，其中我创建了一个结构，称为Point与一个等效的可比较的方法。

How can I do that by modifying the above code? Or is that a better and "clean" way to do this? I also use to pass this code to C++, in which I've created a structure called Point with a equivalent comparable method.

推荐答案

通过 this.y 和的相同比较替换返回0 obj.y 。

Replace return 0 by the same comparison algo on this.y and obj.y.

顺便说一下，在这里不需要重新分配 tmp 优化的图片可以是：

By the way, reassigning to tmp is unnecessary here. The optimized picture can look like:

public int compareTo(Ponto other) {
    if (this.x == other.x) {
        return (this.y < other.y) ? -1 : ((this.y == other.y) ? 0 : 1);
    } else {
        return (this.x < other.x) ? -1 : 1;
    }
}

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