Heapsort

package com.company;

public class MaxHeap {

    private int[] arr;
    private int size;

    public MaxHeap(){
        arr = new int[100];
        size = 0;
    }

    public MaxHeap(int[] arr){
        this.arr = arr;
        size = arr.length;
        for (int i = size/2; i >= 0; i--) {
            heapify(i);
        }
    }

    public int getSize() {
        return size;
    }

    private void heapify(int i){
        int largest = i;
        int l = leftChild(i);
        int r = rightChild(i);
        if(l<size && arr[l] > arr[largest])
            largest = l;
        if(r<size && arr[r] > arr[largest])
            largest = r;
        if(largest != i){
            int temp = arr[i];
            arr[i] = arr[largest];
            arr[largest] = temp;
            heapify(largest);
        }
    }

    private void bubbleUp(int i){
        int p;
        //while I am not the root and I am greater than
        //my parent
        while(i!=0 && arr[(p=parent(i))] < arr[i]){
            int temp = arr[i];
            arr[i] = arr[p];
            arr[p] = temp;
            i = p;
        }
    }

    private int leftChild(int i){
        return 2*i + 1;
    }
    private int rightChild(int i){
        return 2*i + 2;
    }

    private int parent(int i){
        return (i-1)/2;
    }

    public void insert(int x){
        if(size == arr.length){
            int[] temp = new int[size * 2];
            for (int i = 0; i < size; i++) {
                temp[i] = arr[i];
            }
            arr = temp;
        }
        int i = size;
        size++;
        arr[i] = x;
        bubbleUp(i);
    }

    public int getMax(){
        if(size == 0){
            //this is an error
            return -1;
        }
        return arr[0];
    }
    public int extractMax(){
        if(size == 0){
            //this is an error.
            return -1;
        }
        if(size == 1){
            size--;
            return arr[0];
        }
        int max = arr[0];
        arr[0] = arr[size - 1];
        size--;
        heapify(0);
        return max;
    }

}