1. public class MergeSort {
    2.     public static void main(String[] args) {
    3.         int[] arr = {4 , 8 , 9 , 6 , 7 , 3 , 5 , 1 , 2 , 0};
    4.         int length;
    5.         int[] temp = new int[length = arr.length];
    6.         mergeSort(arr,0,length-1,temp);
    7.         System.out.println(Arrays.toString(arr));
    8.     }
    10.     public static void mergeSort(int[] arr , int left , int right , int[] temp) {
    11.         if (left<right) {
    12.             int mid = (left + right) / 2 ;
    13.             mergeSort(arr,left,mid,temp);
    14.             mergeSort(arr,mid+1,right,temp);
    15.             merge(arr,left,right,temp);
    16.         }
    17.     }
    19.     public static void merge(int[] arr , int left , int right , int[] temp) {
    20.         int l = left;
    21.         int mid = (left + right) / 2;
    22.         int r = mid + 1;
    23.         int tempIndex = left;
    26.         while(l <= mid && r <= right) {
    27.             if (arr[l] < arr[r]) {
    28.                 temp[tempIndex] = arr[l];
    29.                 tempIndex++;
    30.                 l++;
    31.             }else {
    32.                 temp[tempIndex] = arr[r];
    33.                 tempIndex++;
    34.                 r++;
    35.             }
    36.         }
    38.         while (l <= mid){
    39.             temp[tempIndex] = arr[l];
    40.             tempIndex++;
    41.             l++;
    42.         }
    44.         while(r <= right) {
    45.             temp[tempIndex] = arr[r];
    46.             tempIndex++;
    47.             r++;
    48.         }
    50.         //if (right + 1 - left >= 0) System.arraycopy(temp, left, arr, left, right + 1 - left);
    51.         for (int i = left; i <= right; i++) {
    52.             arr[i] =temp[i];
    53.         }
    54.     }