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;
}