java的radixsort

Java的radix sort是一种非比较排序算法，它通过将数据按照位数切割成不同的数字，然后按每个位数分别比较来实现排序。以下是Java的radix sort的代码示例：

public static void radixSort(int[] arr) {
    if (arr == null || arr.length < 2) {
        return;
    }
    int max = Integer.MIN_VALUE;
    for (int i = 0; i < arr.length; i++) {
        max = Math.max(max, arr[i]);
    }
    int maxDigit = 0;
    while (max != 0) {
        max /= 10;
        maxDigit++;
    }
    int mod = 10, div = 1;
    ArrayList<ArrayList<Integer>> bucketList = new ArrayList<ArrayList<Integer>>();
    for (int i = 0; i < 10; i++) {
        bucketList.add(new ArrayList<Integer>());
    }
    for (int i = 0; i < maxDigit; i++, mod *= 10, div *= 10) {
        for (int j = 0; j < arr.length; j++) {
            int num = (arr[j] % mod) / div;
            bucketList.get(num).add(arr[j]);
        }
        int index = 0;
        for (int j = 0; j < bucketList.size(); j++) {
            for (int k = 0; k < bucketList.get(j).size(); k++) {
                arr[index++] = bucketList.get(j).get(k);
            }
            bucketList.get(j).clear();
        }
    }
}