StackInterface.java

public interface StackInterface<T>
{
    /**
     * Adds a new entry to the top of this stack.
     * @param newEntry An object to be added to the stack.
     */
    public void push(T newEntry);

    /**
     * Removes and returns this stack's top entry.
     * @return The object at the top of the stack.
     * @throws EmptyStackException if the stack is empty before
     * the operation.
     */
    public T pop();

    /**
     * Retrieves this stack's top entry.
     * @return The object at the top of the stack.
     * @throws EmptyStackException if the stack is empty.
     */
    public T peek();

    /**
     * Detects whether this stack is empty.
     * @return True if the stack is empty.
     */
    public boolean isEmpty();

    /**
     * Removes all entries from this stack.
     */
    public void clear();
    
     /**
     * used for LinkedStack.
     * @param infix an infix to be converted into a postfix
     */
    public void convertToPostfix(String infix);
    
}