Thuật toán sắp xếp merge sort trong Java

public class MergeSortExample {
   public static void main(String[] args) {
      int[] arr = { 3, 1, 4, 2, 7, 5, 8, 6 };
      
      System.out.println("Mảng trước khi sắp xếp: " + Arrays.toString(arr));
      
      mergeSort(arr, 0, arr.length - 1);
      
      System.out.println("Mảng sau khi sắp xếp: " + Arrays.toString(arr));
   }
   
   public static void mergeSort(int[] arr, int left, int right) {
      if (left < right) {
         int middle = (left + right) / 2;
         mergeSort(arr, left, middle);
         mergeSort(arr, middle + 1, right);
         merge(arr, left, middle, right);
      }
   }
   
   public static void merge(int[] arr, int left, int middle, int right) {
      int n1 = middle - left + 1;
      int n2 = right - middle;
      int[] L = new int[n1];
      int[] R = new int[n2];
      
      for (int i = 0; i < n1; ++i)
         L[i] = arr[left + i];
      for (int j = 0; j < n2; ++j)
         R[j] = arr[middle + 1 + j];
         
      int i = 0, j = 0;
      int k = left;
      while (i < n1 && j < n2) {
         if (L[i] <= R[j]) {
            arr[k] = L[i];
            i++;
         } else {
            arr[k] = R[j];
            j++;
         }
         k++;
      }
      
      while (i < n1) {
         arr[k] = L[i];
         i++;
         k++;
      }
      
      while (j < n2) {
         arr[k] = R[j];
         j++;
         k++;
      }
   }
}