This document provides instructions and code examples for creating a memory game application in Java. It discusses displaying cards as JLabels with ImageIcons, using inheritance by extending classes like JPanel and handling click events with LabelListeners to flip the cards over. The document also covers using if/else statements and extending classes to inherit methods while retaining individual attributes and methods.

1. Lab 7 – 8:
Memory Game
The Final Stretch!
Victoria A. Minorczyk
Davis 302 | Thurs 1-1:50
vaminorc@buffalo.edu

2. For Lab 7,
at the start of your program…
Your window should Note:
look something like this. -cards should NOT over
It should contain only lap each other.
TWO cards, showing the -cards should be displayed
back of the card. at 128 pixels by
160 pixels
When you When the
click on a same card is
card, it clicked, it
should flip should flip
over (show back over
the front (show the
of the back of the
card.) card again)

3. A little about ‘extends’ in Java
SYNTAX – How do I write this in my code?
• The keyword extends is to be specified in the HEADER of a CLASS
• It’s syntax is as follows:
<access control modifier> class <class name> extends <class name>
• For example: public class Basketball extends Ball
SEMANTICS – What does it mean?
• When class A extends class B, you may think of class A as a literal extension of class
B
• Class A will retain ALL of it’s own attributes, properties and methods, and…
• Class A will also inherit all of class B’s attributes, properties, and methods.
• Class B does NOT gain any additional attributes, properties, or methods from class
A.
For this lab, your
GameBoard class will extend JPanel.
So…
EVERYTHING that you can do with a JPanel
you can do with your GameBorad!


4. public class BasicMath { public class AdvancedMath extends BasicMath{
public int add(int x, int y) { public int specialFunction(int a, int b){
return x + y;
} /*Notice how the add, mult, and sub methods
are not defined in AdvancedMath. However,
public int sub(int x, int y){ because AdvancedMath extends BasicMath, it
return x - y; inherits all the methods in BasicMath!*/
}
int answer = this.add(a,0);
public int mult(int x, int y){ answer = this.mult(answer, 2);
return x*y; answer = this.sub(answer, b);
}
return answer;
public void printAns(int x){ }
System.out.println("The answer is: " + x);
} }
}

5. public class Calculations { public class Computer {
public static void main(String[] args){ private BasicMath _b;
AdvancedMath calculator = new AdvancedMath(); public Computer(BasicMath b){
//AdvancedMath has specialFunction defined _b = b;
int a = calculator.specialFunction(5,2); }
int b = calculator.specialFunction(8,3);
}
/*Notice how the printAns method is defined in
* the BasicMath class and is NOT defined in the
* AdvancedMath class. However, we can still invoke
* the printAns method on an AdvancedMath object
* because AdvancedMath extends BasicMath.*/
calculator.printAns(a);
calculator.printAns(b);
/*Notice that the parameter for a Computer is a
* BasicMath object However, it is acceptable to
* use an AdvanceMath object, because AdvancedMath
* extends BasicMath*/
Computer comp = new Computer(new AdvancedMath());
}
}

6. Displaying Images
ImageIcon Objects:
• Use javax.swing.ImageIcon objects to display images
• When instantiating an ImageIcon object, you must supply a path name as an
argument. For example…
• new ImageIcon(“FolderName/PackageName/FileName.jpg”);
• HOWEVER, you can NOT add an ImageIcon oject directly to a JPanel object
Adding Images to a JPanel:
*Recall* - You can add JLabel objects directly to a JPanel object
• Use a JLabel to hold your ImageIcon objects!
*Recall* - JLabel has a ‘setText’ method to change the text the JLabel displays
• Use the JLabel ‘setIcon’ method to change the Icon the JLabel displays

7.  Awesome If-Else Statements 
Syntax:
if ( <condition> ) {
<if-body>
}
else {
<else-body>
}
Semantics:
If the condition is TRUE, only the if-body is executed.
If the condition is FALSE, only the else-body is executed.

8.  Awesome If-Else Statements 
public class IfElseClass {
public static void main (String[] args){
int x = -5;
int y = 1;
if (x < y){
//Executes ONLY when condition is TRUE
System.out.println("Condition was TRUE. " + x + " is less than " + y);
}
else{
//Executes ONLY when condition is FALSE
System.out.println("Condition was FALSE. " + x + " is not less than " + y);
}.

9. Overview
GameBoard
• Extends JPanel class
• Responsible for putting two cards to itself
Card
• Responsible for keeping track of two ImageIcons (one for
face-up image and one for face-down image)
• Responsible for knowing if the Card is face-up or face-
down
LableListener
• Handles events for the “cards” or the JLables
• When a card is clicked, the IconImage on the JLable
should change.