Merge Sort Java Code

 package com.imaginea.ds.practice;  
 /*  
  *MergeSort  
  *     Worst case performance     O(n log n)  
  *     Best case performance     O(n log n) typical,     O(n) natural variant  
  *     Average case performance     O(n log n)  
  *     Worst case space complexity     O(n) auxiliary  
  */  
 public class MergeSortExample {  
      static int[] arr = {45,23,11,89,77,98,4,28,65,43};  
      public static void main(String[] args) {  
           doMergeSort(0, arr.length-1);  
           for(int num:arr){  
                System.out.print(num+" ");  
           }  
      }  
      private static void doMergeSort(int lowerIdx, int higherIdx){  
           if(lowerIdx < higherIdx){  
                int middleIdx = lowerIdx + (higherIdx - lowerIdx)/2;  
                doMergeSort(lowerIdx, middleIdx);  
                doMergeSort(middleIdx+1, higherIdx);  
                mergeArray(lowerIdx, middleIdx, higherIdx);  
           }  
      }  
      private static void mergeArray(int lowerIdx, int middleIdx, int higherIdx){  
           int i=lowerIdx;       
           int j=middleIdx+1;  
           int k=lowerIdx;  
           int[] tmpArr= new int[higherIdx+1];  
           for(int idx=lowerIdx;idx<=higherIdx; idx++){  
                tmpArr[idx]=arr[idx];  
           }  
           while(i<=middleIdx && j<=higherIdx){  
                if(tmpArr[i] <= tmpArr[j]){  
                     arr[k]=tmpArr[i];  
                     i++;  
                }else{  
                     arr[k]=tmpArr[j];  
                     j++;  
                }  
                k++;  
           }  
           while(i <= middleIdx){  
                arr[k]=tmpArr[i];  
                k++;  
                i++;  
           }  
      }  
 }