added merge sort in Java language

Author: berenyihenrik

sortingAlgo/mergeSort/mergeSort.java

@@ -0,0 +1,43 @@
+public class mergeSort {
+    public static void merge(int[] array_1, int low, int mid, int high) {
+        int i = low;
+        int j = mid + 1;
+        int k = 0;
+
+        int[] array_2 = new int[high - low + 1];
+
+	    while(i <= mid && j <= high) {
+		    if(array_1[i] <= array_1[j]) {
+			    array_2[k] = array_1[i];
+			    k += 1; i += 1;
+		    }
+		    else {
+			    array_2[k] = array_1[j];
+			    k += 1; j += 1;
+		    }
+	    }
+ 
+	    while(i <= mid) {
+		    array_2[k] = array_1[i];
+		    k += 1; i += 1;
+	    }
+
+	    while(j <= high) {
+		    array_2[k] = array_1[j];
+		    k += 1; j += 1;
+	    }
+
+	    for(i = low; i <= high; i += 1) {
+		    array_1[i] = array_2[i - low];
+	    }
+    }
+
+    public static void sort(int[] array, int low, int high) {
+        if(low < high) {
+            int mid = (low + high) / 2;
+            sort(array, low, mid);
+            sort(array, mid + 1, high);
+            merge(array, low, mid, high);
+        }  
+    }      
+}