find K maximum value from an unsorted array(implement min heap)

Maintain a min-heap with size = k, to collect the result.

 //Find K minimum values from an unsorted array
 //Implement Min-Heap

 public int[] findKMax(int[] arr, int k){
     if(arr == null || arr.length == 0) return null;
     int[] result = new int[k];
     for(int i = 0; i < k; i ++)
         result[i] = arr[i];
     buildMinHeap(result);
     for(int i = k; i < arr.length; i ++){
         if(arr[i] > result[0]){
             result[0] = arr[i];
             minHeapify(result, 0);
         }
     }
     return result;
 }

 public void buildMinHeap(int[] arr){
     for(int i = arr.length / 2 - 1; i > -1; i --){//bottom-up build min heap
         minHeapify(arr, i);
     }
 }

 public void minHeapify(int[] arr, int curIndex){
     int left = curIndex * 2 + 1;
     int right = curIndex * 2 + 2;
     int smallest = curIndex;
     if(left < arr.length && arr[left] < arr[smallest])
         smallest = left;
     if(right < arr.length && arr[right] < arr[smallest])
         smallest = right;
     if(smallest != curIndex){
         swap(arr, smallest, curIndex);
         minHeapify(arr,smallest);
     }
 }

 public void swap(int[] arr, int aa, int bb){
     int tmp = arr[aa];
     arr[aa] = arr[bb];
     arr[bb] = tmp;
 }