import java.util.Stack;

/**
 * A second attempt at creating a VehicleStack by <i>"wrapping"</i> the Stack 
 * type and forwarding its method calls.
 * <p>
 * This class provides type checking during compile time for all stack methods.
 * This type checking insures that an Object which is not a Vehicle cannot be
 * used with <i>any</i> of the VehicleStack methods. If an attempt is made to 
 * use a non-Vehicle type with a VehicleStack method, the program will fail to 
 * compile and the compiler indicate a type check error.
 * <p>
 * This is know as <i>strong</i> type checking. However, our class no longer
 * extends the Stack class, so the following code will not compile
 * <pre>
 *     Stack s = new VehicleStack();
 *
 *     s.push(new Vehicle());
 *     Vehicle v = s.pop();
 * </pre>
 * Since VehicleStack no longer extends Stack we cannot use it in place of a
 * an ordinary stack.
 *
 * @version 2.0
 * @author  John Kloss
 */

public class VehicleStackTwo {

    Stack s = new Stack();

    /**
     * Creates a new instance of VehicleStackTwo.
     */
    public VehicleStackTwo() {

    }


    /**
     * Tests if this VehicleStack is empty. 
     *
     * @return           Returns <code>true</code> if this VehicleStack is
     *                   empty; <code>false</code> otherwise.
     */
    public boolean empty() {
	return s.empty();
    }


    /**
     * Looks at the Vehicle at the top of this VehicleStack without removing 
     * it from the stack. 
     *
     * @return           The Vehicle at the top of this VehicleStack.
     *
     * @exception        EmptyStackException  Thrown if this VehicleStack is 
     *                   empty.  
     */
    public Vehicle peek() {
	return (Vehicle) s.peek();
    }

    
    /**
     * Removes the Vehicle at the top of this VehicleStack and returns that 
     * Vehicle.
     *
     * @return           The Vehicle at the top of this VehicleStack. 
     *
     * @exception        EmptyStackException  Thrown if this VehicleStack is
     *                   empty.
     */
    public Vehicle pop() {
	return (Vehicle) s.pop();
    }


    /**
     * Pushes a Vehicle onto the top of this stack.
     *
     * @param obj        A Vehicle to be pushed onto this stack.
     *
     * @return           The Vehicle argument.
     */
    public Vehicle push(Vehicle obj) {
	return (Vehicle) s.push(obj);
    }


    /**
     * Returns where a Vehicle is on this stack.
     *
     * @param obj        A Vehicle to search for in this stack.
     *
     * @returns          The distance from the top of this stack where the 
     *                   Vehicle is located. A return value of -1 indicates
     *                   that the Vehicle is not on this stack. 
     */
    public int search(Vehicle obj) {
	return s.search(obj);
    }
}