/** 
 * An interface for the Stack ADT, adapted from Frank Carrano.
 * @author Jadrian Miles
 */
public interface Stack<T> {
    /**
     * Adds an item to the top of this stack.
     * @param item The item to add.
     */
    public void push(T item);
    
    /**
     * Removes and returns the item from the top of this stack.
     * @return the item at the top of the stack, or null if empty.
     */
    public T pop();
    
    /**
     * Returns the item on top of the stack, without removing it.
     * @return the item at the top of the stack, or null if empty.
     */
    public T peek();
    
    /** Returns whether the stack is empty. */
    public boolean isEmpty();
    
    /** Removes all items from the stack. */
    public void clear();
}