Adding merge sort algorithm in java

Algorithm/merge_sort.java

@@ -0,0 +1,88 @@
+import java.util.Arrays;
+
+// Merge sort in Java
+
+class Main {
+
+  // Merge two sub arrays L and M into array
+  void merge(int array[], int p, int q, int r) {
+
+    int n1 = q - p + 1;
+    int n2 = r - q;
+
+    int L[] = new int[n1];
+    int M[] = new int[n2];
+
+    // fill the left and right array
+    for (int i = 0; i < n1; i++)
+      L[i] = array[p + i];
+    for (int j = 0; j < n2; j++)
+      M[j] = array[q + 1 + j];
+
+    // Maintain current index of sub-arrays and main array
+    int i, j, k;
+    i = 0;
+    j = 0;
+    k = p;
+
+    // Until we reach either end of either L or M, pick larger among
+    // elements L and M and place them in the correct position at A[p..r]
+    // for sorting in descending
+    // use if(L[i] >= <[j])
+    while (i < n1 && j < n2) {
+      if (L[i] <= M[j]) {
+        array[k] = L[i];
+        i++;
+      } else {
+        array[k] = M[j];
+        j++;
+      }
+      k++;
+    }
+
+    // When we run out of elements in either L or M,
+    // pick up the remaining elements and put in A[p..r]
+    while (i < n1) {
+      array[k] = L[i];
+      i++;
+      k++;
+    }
+
+    while (j < n2) {
+      array[k] = M[j];
+      j++;
+      k++;
+    }
+  }
+
+  // Divide the array into two sub arrays, sort them and merge them
+  void mergeSort(int array[], int left, int right) {
+    if (left < right) {
+
+      // m is the point where the array is divided into two sub arrays
+      int mid = (left + right) / 2;
+
+      // recursive call to each sub arrays
+      mergeSort(array, left, mid);
+      mergeSort(array, mid + 1, right);
+
+      // Merge the sorted sub arrays
+      merge(array, left, mid, right);
+    }
+  }
+
+  public static void main(String args[]) {
+
+    // created an unsorted array
+    int[] array = { 6, 5, 12, 10, 9, 1 };
+
+    Main ob = new Main();
+
+    // call the method mergeSort()
+    // pass argument: array, first index and last index
+    ob.mergeSort(array, 0, array.length - 1);
+
+    System.out.println("Sorted Array:");
+    System.out.println(Arrays.toString(array));
+  }
+}