Added java implementation of merge sort (#22581)

guide/english/algorithms/sorting-algorithms/merge-sort/index.md

@@ -252,3 +252,66 @@ temp = [None for _ in range(len(arr))]
 merge_sort(arr, 0, len(arr) - 1)
 print(arr, inversions)
 ```
+
+### Implementation in Java
+```java
+public class mergesort {
+
+	public static int[] mergesort(int[] arr,int lo,int hi) {
+		
+		if(lo==hi) {
+			int[] ba=new int[1];
+			ba[0]=arr[lo];
+			return ba;
+		}
+		
+		int mid=(lo+hi)/2;
+		int arr1[]=mergesort(arr,lo,mid);
+		int arr2[]=mergesort(arr,mid+1,hi);
+		return merge(arr1,arr2);
+	}
+	
+	public static int[] merge(int[] arr1,int[] arr2) {
+		int i=0,j=0,k=0;
+		int n=arr1.length;
+		int m=arr2.length;
+		int[] arr3=new int[m+n];
+		while(i<n && j<m) {
+			if(arr1[i]<arr2[j]) {
+				arr3[k]=arr1[i];
+				i++;
+			}
+			else {
+				arr3[k]=arr2[j];
+				j++;
+			}
+			k++;
+		}
+		
+		while(i<n) {
+			arr3[k]=arr1[i];
+			i++;
+			k++;
+		}
+		
+		while(j<m) {
+			arr3[k]=arr2[j];
+			j++;
+			k++;
+		}
+		
+		return arr3;
+		
+	}
+	
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+		int arr[]= {2,9,8,3,6,4,10,7};
+		int[] so=mergesort(arr,0,arr.length-1);
+		for(int i=0;i<arr.length;i++)
+			System.out.print(so[i]+" ");
+	}
+
+}
+
+```