public class ArrayStack					// Array implementation of a stack, since we are using an array, we cannot store a Generic, so we will just make it an array of ints
{
	private int[] stack;				// our stack
	private int top;					// index of the current top of the stack
	
	public ArrayStack()					// no size, set it to 100, top is initially -1
	{
		stack=new int[100];
		top=-1;
	}
	
	public ArrayStack(int size)			// user gave us a size, this limits the array to a reasonable amount but we will have full stacks if top==size
	{
		stack=new int[size];
		top=-1;
	}
	
	public int peek() throws StackEmptyException		// return top of stack (if empty, throw exception)
	{
		if(top==-1) throw new StackEmptyException("Stack is empty, cannot peek");
		else return stack[top];
	}

	public int pop() throws StackEmptyException		// return top of stack and reduce top by 1 for new top of stack
	{
		if(top==-1) throw new StackEmptyException("Stack is empty, cannot pop");
		else 
		{
			int temp=stack[top];
			top--;
			return temp;
		}
	}	
		
	public boolean isEmpty()					// stack is empty if top is -1 as top will be the index of the top of stack, between 0 and size-1
	{
		return top==-1;
	}
	
	public boolean isFull()						// unlike the linked list implementation, the array implementation can be full (unless we implement array doubling)
	{											// full occurs once top==size-1
		return top==stack.length-1;
	}
	
	public void push(int x) throws StackFullException		// add x onto stack at position top+1 as long as stack is not yet full
	{
		if(top==stack.length-1) throw new StackFullException("Cannot push " + x + " onto full stack");
		else
		{
			top++;
			stack[top]=x;
		}
	}
}