如何实现归并排序算法？

归并排序是一种基于分治法的排序算法，其基本思想是将数组分为两个子数组，分别排序，然后合并两个子数组。

以下是一个简单的归并排序实现：

public static void mergeSort(int[] arr, int left, int right) {
    if (left >= right) {
        return;
    }
    int mid = left + (right - left) / 2;
    mergeSort(arr, left, mid);
    mergeSort(arr, mid + 1, right);
    merge(arr, left, mid, right);
}

private static void merge(int[] arr, int left, int mid, int right) {
    int[] temp = new int[right - left + 1];
    int i = left;
    int j = mid + 1;
    int k = 0;
    while (i <= mid && j <= right) {
        if (arr[i] <= arr[j]) {
            temp[k++] = arr[i++];
        } else {
            temp[k++] = arr[j++];
        }
    }
    while (i <= mid) {
        temp[k++] = arr[i++];
    }
    while (j <= right) {
        temp[k++] = arr[j++];
    }
    for (int l = 0; l < temp.length; l++) {
        arr[left + l] = temp[l];
    }
}