Stack using queue

import java.util.* ;
import java.io.*; 
public class Stack {

    // Define the data members.
    private Deque<Integer>queue1;


    public Stack() {
        // Implement the Constructor.
        queue1=new ArrayDeque<Integer>();
    }



    /*----------------- Public Functions of Stack -----------------*/


    public int getSize() { 
        // Implement the getSize() function.
        return queue1.size();
    }

    public boolean isEmpty() {
        // Implement the isEmpty() function.
        if(queue1.isEmpty())
        return true;
        return false;
    }

    public void push(int element) {
        // Implement the push(element) function.
        queue1.push(element);
    }

    public int pop() {
        // Implement the pop() function.
        if(isEmpty())
        return -1;
        return queue1.poll();
    }

    public int top() {
        // Implement the top() function.
        if(isEmpty())
        return -1;
        return queue1.getFirst();
    }
}