Exercises, class 4

1.
a) Put yourself in the following situation:

• You are tasked with coding a management system for a donut store – such as Tim Hortons or
Dunkin Donuts.

• You have to create two interfaces:
◦ Exchangeable, with two methods:

▪ give()
▪ receive()

◦ Actable, with one method:
▪ act()

• You have to create four classes:
◦ Employee
◦ Customer
◦ Money
◦ Donut

Each class has to implement one of the interfaces. Choose wisely!

b) For every class, explain why you made it implement that specific interface.

2. Here is an interface for implementing methods that print messages to the screen:

public interface Printable {
private void printToScreen(String msg){
System.out.println(msg);
}
}

What is wrong with that interface?

Exercises, class 3

1. Here is Java code to create a chess piece:

public class ChessPiece {
public String pieceName;
public String position;

public ChessPiece(String pieceName, String position){
this.pieceName = pieceName;
this.position = position;
}
}

a) Make this class abstract and add an abstract method to it, called move.

b) Take each of the classes from last exercise and have it implement the move method.

Note: the body of the concrete classes’ methods will only contain code to print “Movement!” to the
screen.

2.

a) Create an abstract class called Room.

This class has 3 attributes:
 xCoordinate
 yCoordinate
 zCoordinate

You will have to decide the type of these attributes.

The Room class also has an abstract method called open, and another abstract method called
close.

b) Create two concrete classes that are children of the Room class, called Kitchen and Bedroom. A
concrete class (representing concrete rooms) has 2 additional attributes in addition to the
attributes of its parent class.

Also, when a concrete class implements the open method, it contains code to print the message
“Room [insert number here] opened!” and when it implements the close method, it contains code
to print the message “Room [insert number here] closed!”