import java.util.*;			// for ArrayList

public class GenericStackWithMultiply<E> // example of creating a Generic Stack by implementing a Generic ArrayList
{
   private ArrayList<E> stack;		// our instance datum
   
   public GenericStackWithMultiply()
   {
		stack=new ArrayList<E>();		// instantiate an empty ArrayList of type E (the "E" is not needed here)
   }
   
   public int getSize() 				// use ArrayList's size method to get the current size of the stack
   {
		return stack.size();
   }
   
   public E peek() 						// peek returns the top element, which is of type E
   {									// this element will be located at the end of the ArrayList
		return stack.get(stack.size()-1);	// at index size-1
   }
   public E pop() 						// we need to get the top element (at size-1) and return it, removing
   {									// this element
		E returnItem=stack.get(stack.size()-1);	// the element is of type E
		stack.remove(stack.size()-1);	// the remove operation does not return the item, so we have to get the item
		return returnItem;					// and then remove it
   }
   
   public void push(E newItem) 			// add new item of type E to the stack
   {
		stack.add(newItem);				// add inserts the item at the end (at location size)
   }
   
   public boolean isEmpty() 			// determine if stack is empty
   {
		return stack.isEmpty();
   }
   
   public static <E> double multiply(GenericStackWithMultiply<? extends Number> s1, GenericStackWithMultiply<? extends Number> s2)
   {
   		double temp=0;
   		int smaller=s1.getSize();
   		if(s2.getSize()<smaller) smaller=s2.getSize();
   		for(int i=0;i<smaller;i++)
   			temp=s1.pop().doubleValue()*s2.pop().doubleValue();
   		return temp;
   }
   
   public static <E> GenericStackWithMultiply<Double> multiplyStacks(GenericStackWithMultiply<? extends Number> s1,
   			GenericStackWithMultiply<? extends Number> s2)
   	{
   		GenericStackWithMultiply<Double> temp=new GenericStackWithMultiply<>();
   		int smaller=s1.getSize();
   		if(s2.getSize()<smaller) smaller=s2.getSize();
   		for(int i=0;i<smaller;i++)
   			temp.push(s1.pop().doubleValue()*s2.pop().doubleValue());
   		return temp;
   	}
   
   // some stack implementations include a isFull method, but with an ArrayList, we assume it is never full
}