分而治之归并排序java

public class MergeSort {

public static void mergeSort(int[] arr, int left, int right) {
if (left < right) {
int mid = (left + right) / 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];
i++;
} else {
temp[k] = arr[j];
j++;
}
k++;
}

while (i <= mid) {
temp[k] = arr[i];
i++;
k++;
}

while (j <= right) {
temp[k] = arr[j];
j++;
k++;
}

for (int p = 0; p < temp.length; p++) {
arr[left + p] = temp[p];
}
}

public static void main(String[] args) {
int[] arr = { 23, 45, 12, 78, 90, 34, 67, 56, 33 };
mergeSort(arr, 0, arr.length - 1);
System.out.println(Arrays.toString(arr));
}

}