Priority Queues:Max Priority Queue

import java.util.ArrayList;
/*************
 * Following is the main function for your reference which we are using internally.

 public static void main(String[] args) {
		PriorityQueue pq = new PriorityQueue();
		int choice = s.nextInt();
		while(choice != -1) {
			switch(choice) {
				case 1 : // insert
					int element = s.nextInt();
					pq.insert(element);
					break;
				case 2 : // getMax
					System.out.println(pq.getMax());
					break;
				case 3 : // removeMax
					System.out.println(pq.removeMax());
					break;
				case 4 : // size
					System.out.println(pq.getSize());
					break;
				case 5 : // isEmpty
					System.out.println(pq.isEmpty());
				default :
						return;
			}
			choice = s.nextInt();
		}
	}
************/

public class PriorityQueue {
    ArrayList<Integer> heap;
    public PriorityQueue(){
        heap=new ArrayList<>();
    }
    int getSize(){
        return heap.size();
    }
    boolean isEmpty(){
        return heap.size()==0;
    }
    int getMax(){
        if(isEmpty())
            return Integer.MIN_VALUE;
        return heap.get(0);
    }
    void insert(int element){
        heap.add(element);
        int childindex=heap.size()-1;
        int parentindex=(childindex-1)/2;
        //upheapify------
        while(childindex>0){
            if(heap.get(childindex)>heap.get(parentindex))
            {
                int temp=heap.get(parentindex);
                heap.set(parentindex,heap.get(childindex));
                heap.set(childindex,temp);
                childindex=parentindex;
                parentindex=(childindex-1)/2;
            }
            else
                return;
        }
    }
    int removeMax(){
        if(isEmpty())
            return Integer.MIN_VALUE;
        int lchildindex=1;
        int rchildindex=2;
        int parentindex=0;
        int maxindex=parentindex;
        int temp=heap.get(0);
        heap.set(0,heap.get(heap.size()-1));
        heap.remove(heap.size()-1);
        while(lchildindex<heap.size()){
        if(heap.get(lchildindex)>heap.get(parentindex))
            maxindex=lchildindex;
        if(rchildindex<heap.size() && heap.get(rchildindex)>heap.get(maxindex))
            maxindex=rchildindex;
        if(maxindex==parentindex)
            break;
        else{
            int temp1=heap.get(parentindex);
            heap.set(parentindex,heap.get(maxindex));
            heap.set(maxindex,temp1);
            parentindex=maxindex;
            lchildindex=2*parentindex +1;
            rchildindex=2*parentindex +2;

        }
        }
         return temp; 
    }


}