自定义排序java数组 [英] custom sorting a java array

问题描述

我有一个[]有一些数字（距某点的距离）。

我想在第一个数组中创建一个索引数组，其中索引按距离排序。

I have an [] that has some numbers (distances from some point).
I want to create an array of indexes into the first array where the indexes are sorted by the distance.

例如

假设 double [] dist = new double [5] {3.2， 7.3，2.2，9.1};

然后我想得到一个这样的数组：

suppose double[] dist=new double[5] {3.2, 1.4, 7.3, 2.2, 9.1};
then I want to get an array like this:

int [] sortedIndexes = new int [5] {1，3，0，2，4};

第二最近的距离我可以检查dist [sortedIndexes [1]]。

我不想排序原始数组，只是基于距离的索引数组。

so if I want the second nearest distance I can check dist[sortedIndexes[1]].
I don't want to sort the original array, just the array of indexes based on the distances.

更新1：
我正在尝试的代码看起来像这样：

UPDATE 1: The Code I was trying looks like this:

Collections.sort(sortedIDXs, new Comparator<Integer>() {
    public int compare(int idx1, int idx2) {
        return Double.compare(distances[idx1], distances[idx2]);
    }
});

但是我遇到了几个错误，最有问题的是：

But I am getting several errors with it with the most "problematic" one being: "Cannot refer to a non-final variable distances inside an inner class defined in a different method"

感谢您使用不同方法定义的内部类中不能引用非最终变量距离

Thanks

推荐答案

您在正确的轨道上，但

• 如果使用 Integer 数组比使用 int 数组更好一个通用的 Comparator< Integer> 。


• 你必须使用 Arrays.sort Collections.sort 用于排序数组。



• 匿名内部类。

• You're better off with an Integer array than an int array if you're using a generic Comparator<Integer>.
• You have to use Arrays.sort instead Collections.sort for sorting an array.

• You have to make the distances variable final if it's referenced in an anonymous inner class.

final double[] distances=new double[]{3.2, 1.4, 7.3, 2.2, 9.1};
Integer[] sortedIDXs  = new Integer[]{0,1,2,3,4};
Arrays.sort(sortedIDXs, new Comparator<Integer>() {
    public int compare(Integer idx1, Integer idx2) {
        return Double.compare(distances[idx1], distances[idx2]);
    }
});

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