Handout June 26, 2003

Interfaces

143 Sections AB/AE

Name:

True or False:

1. The following statements are legal, given the following definition:

public interface ICityEmployee{…}

public class Mayor implements ICityEmployee, IElectedEmployee{…}

a) An interface cannot have member variables

b) Variables, arguments and results can have interfaces as their type

c) ICityEmployee myMayor=new Mayor();

d) IElectedEmployee myMayor=new Mayor();

e) Mayor myMayor=new ICityEmployee();

f) IElectedEmployee myMayor=new IElectedEmployee();

g) Class Mayor needs to implement all methods declared in ICityEmployee

h) Class Mayor needs to implement all methods declared in ICityEmployee, but not all the ones declared in IElectedEmployee

i) Class Mayor can only have methods declared in ICityEmployee and IElectedEmployee

j) An object of class Mayor is a valid argument to the following funcion:

public double getEmployeeSalary(ICityEmployee employee)

k) An object of class Mayor is a valid argument to the following funcion:

public int getTermLength(IElectedEmployee employee)

l) Interfaces can have private methods

2. Consider the following problem:

You and your neighbor (by seat) are asked to design a chess game. You have procrastinated until the last minute and now it is imperative that you split the coding burden in order to finish on time. You need to:

• Agree on a set of classes and a class hierarchy of your system. List the classes that you identified and (very briefly) the responsibilities of each class.
• Agree on a set of methods that your classes will expose (you will need to use classes developed by your neighbor, but you want have access to the actual implementation since you will be working in parallel)

Suggested Design (note many others are possible and valid):

Notice the commonality between the game pieces and define a common interface for these.

Provide a class Board that abstracts the physical represenation of the board.

Sample JavaDoc comment for a method—let’s take move(..) in interface Piece:

/**

* This method moves the piece from its current position to

* The position specified by the method parameters

* The piece needs to notify the board of its new position

* by calling updatePiecePosition

* @param newXPos the new row position of the piece

* @param newYPos the new column position of the piece

* @return true if the move is legal and the piece moved, false otherwise

*/