Credit to Steinberg and Palmer, from their book:

The code provided below displays nine panels of different colors in a 3 X 3 grid. Whenever the mouse enters a panel, it turns magenta; when the mouse leaves, the color reverts back to its original color. Add the following user story: "When the user clicks on the center panel, the colors of the eight surrounding panels rotate to the next panel in a clockwise direction." Remember to TDD.

When complete, add this user story: "When the user consecutively clicks on two of the outer panels, the colors of these panels are swapped."

I (Boris) have typed out the code that the book provides (Init, MyJPanel). I have also written some tests that were absent from the book (MyJPanelTest).

I have created a test in InitTest to get you started (it's currently failing, obviously). It's a poor quality test. I expect you to improve upon it and add more tests, as needed, for you to feel comfortable that your code works.

I have created CenterPanel to get you started as well. Since Init has the panels, CenterPanel will need to call Init to do the logic. I added a clicked() method.

I used JUnit 5, not 4. So I am using Jupiter imports. I recommend you create a new Eclipse Project, create a "test" source folder, copy the 2 test files into "test", copy the 3 source files into "src" and add JUnit 5 to your build path.

CenterPanel.java

import java.awt.Color;

@SuppressWarnings("serial")

public class CenterPanel extends MyJPanel {

Init init;

public CenterPanel(Color myColor, Init init) {

super(myColor);

this.init = init;

}

@Override

public void clicked() {

}

}

Init.java

import java.awt.Color;

import java.awt.GridLayout;

import javax.swing.JFrame;

public class Init {

public JFrame jFrame;

MyJPanel panels[];

Color colors[] = { Color.blue, Color.green, Color.red, Color.white,

Color.yellow, Color.black, Color.orange,

Color.cyan, Color.gray };

public Init() {

panels = new MyJPanel[9];

jFrame = new JFrame("NINE SQUARES PROGRAM");

jFrame.setSize(500, 500);

jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

jFrame.getContentPane().setLayout(new GridLayout(3, 3));

for (int i = 0; i < panels.length; i++) {

panels[i] = new MyJPanel(colors[i]);

jFrame.getContentPane().add(panels[i]);

}

jFrame.setVisible(true);

}

public static void main(String[] args) {

new Init();

}

}

MyJPanel.java

import java.awt.Color;

import java.awt.event.MouseAdapter;

import java.awt.event.MouseEvent;

import javax.swing.JPanel;

@SuppressWarnings("serial")

public class MyJPanel extends JPanel {

private Color myColor;

public MyJPanel(Color myColor) {

this.myColor = myColor;

setBackground(myColor);

addMouseListener(new MouseWatcher());

}

public void setMyColor(Color myColor) {

this.myColor = myColor;

setOriginalColor();

}

public void setSelectedColor() {

setBackground(Color.magenta);

}

public void setOriginalColor() {

setBackground(myColor);

}

class MouseWatcher extends MouseAdapter {

@Override

public void mouseEntered(MouseEvent me) {

setSelectedColor();

}

@Override

public void mouseExited(MouseEvent me) {

setOriginalColor();

}

@Override

public void mouseClicked(MouseEvent me) {

clicked();

}

}

public void clicked() {

}

}

InitTest.java

import static org.junit.Assert.assertSame;

import org.junit.jupiter.api.BeforeEach;

import org.junit.jupiter.api.Test;

class InitTest {

Init init;

@BeforeEach

public void setUp() {

init = new Init();

}

@Test

public void rotating_colors() {

init.panels[4].clicked();

assertSame(init.colors[3],

init.panels[0].getBackground());

assertSame(init.colors[0],

init.panels[1].getBackground());

assertSame(init.colors[1],

init.panels[2].getBackground());

assertSame(init.colors[6],

init.panels[3].getBackground());

assertSame(init.colors[2],

init.panels[5].getBackground());

assertSame(init.colors[7],

init.panels[6].getBackground());

assertSame(init.colors[8],

init.panels[7].getBackground());

assertSame(init.colors[5],

init.panels[8].getBackground());

}

}

MyJPanelTest.java

import static org.junit.Assert.assertSame;

import java.awt.Color;

import org.junit.jupiter.api.BeforeEach;

import org.junit.jupiter.api.Test;

class MyJPanelTest {

private static final Color COLOR = Color.BLACK;

private static final Color MAGENTA = Color.magenta;

MyJPanel myJPanel;

@BeforeEach

public void setUp() {

myJPanel = new MyJPanel(COLOR);

}

@Test

void set_selected_color() {

myJPanel.setSelectedColor();

assertSame(MAGENTA, myJPanel.getBackground());

}

@Test

void set_original_color() {

myJPanel.setOriginalColor();

assertSame(COLOR, myJPanel.getBackground());

}

}