Stack implementation using arrays

Stack.java

import java.util.EmptyStackException;

public class Stack<Key> implements StackADT<Key> {

	public Key[] data;  // array-based implementation of the stack
	final int INITIAL_SIZE = 8;
	
	int top = 0;
	
	@SuppressWarnings("unchecked")
	public Stack() {
		data = (Key[]) new Object[INITIAL_SIZE];
	}
	
	@SuppressWarnings("unchecked")
	public Stack(int n) {
		data = (Key[]) new Object[n];
	}
	
	@Override
	public boolean isEmpty() {
		return (top == 0);
	}

	@Override
	public boolean isFull() {
		return (top == data.length);
	}

	@Override
	public void push(Key key) {
		if (!isFull()) {
			this.data[top] = key;
			top++;
		} 
		else {
			// dynamically reallocate the array
			@SuppressWarnings("unchecked")
			Key[] dataCopy = (Key[]) new Object[top*2];
			for (int i = 0; i < this.data.length; i++) {
				dataCopy[i] = data[i];
			}
			this.data = dataCopy;
			push(key);
		}
		
	}

	@Override
	public Key pop() {
		if (!isEmpty()) {
			Key result = data[top];
			top--;
			return result;
		} {
			throw new EmptyStackException();
		}
		
	}

	@Override
	public Key top() {
		if (!isEmpty()) {
			Key result = data[top];
			return result;
		} {
			throw new EmptyStackException();
		}
	}
	
	
	@Override
	public String toString() {
		StringBuilder sbBuilder = new StringBuilder();

		sbBuilder.append("Stack of size: " + this.top +"\n");
		for (int i = 0; i < top; i++) {
			sbBuilder.append(this.data[i]+" ");
		}
		return new String(sbBuilder);
	}
	
	public static void main(String[] args) {
		Stack<Integer> s = new Stack<Integer>();
		s.push(21);
		s.push(71);
		s.push(3);
		s.push(8);
		System.out.println(s);
	}

}