diff --git a/src/main/java/chapter06/bmi/Bmi.java b/src/main/java/chapter06/bmi/Bmi.java
index cb191ef..7746c15 100644
--- a/src/main/java/chapter06/bmi/Bmi.java
+++ b/src/main/java/chapter06/bmi/Bmi.java
@@ -1,65 +1,75 @@
-package chapter06.bmi;// Code written as part of the Java-Methods-Program-AP-Comp-A-2021-2022 repository on GitHub.
+// Code written as part of the Java-Methods-Program-AP-Comp-A-2021-2022 repository on GitHub.
+package chapter06.bmi;
+
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.text.DecimalFormat;
-public class Bmi extends JFrame
- implements ActionListener
-{
- JTextField inputLbs, inputInches, displayBmi;
+/**
+ * A {@link JFrame} window that calculates BMI from pounds and inches.
+ */
+public class Bmi extends JFrame implements ActionListener {
+ private JTextField massInputField;
+ private JTextField heightInputField;
+ private JTextField bmiDisplayField;
- public Bmi()
- {
- super("BMI Calculator");
- JLabel labelLbs = new JLabel("Weight (lbs):", SwingConstants.RIGHT);
- inputLbs = new JTextField(5);
- JLabel labelInches = new JLabel("Height (inches):", SwingConstants.RIGHT);
- inputInches = new JTextField(5);
- JLabel labelBmi = new JLabel("BMI = ", SwingConstants.RIGHT);
- displayBmi = new JTextField(5);
- displayBmi.setEditable(false);
- JButton go = new JButton("Compute");
- go.addActionListener(this);
+ public Bmi() {
+ super("BMI Calculator");
+ JLabel labelLbs = new JLabel("Weight (lbs.):", SwingConstants.RIGHT);
+ massInputField = new JTextField(5);
+ JLabel labelInches = new JLabel("Height (in.):", SwingConstants.RIGHT);
+ heightInputField = new JTextField(5);
+ JLabel labelBmi = new JLabel("BMI = ", SwingConstants.RIGHT);
+ bmiDisplayField = new JTextField(5);
+ bmiDisplayField.setEditable(false);
+ JButton go = new JButton("Compute");
+ go.addActionListener(this);
- Container c = getContentPane();
- c.setBackground(Color.white);
- JPanel p = new JPanel();
- p.setLayout(new GridLayout(3, 2, 5, 5));
- p.add(labelLbs);
- p.add(inputLbs);
- p.add(labelInches);
- p.add(inputInches);
- p.add(labelBmi);
- p.add(displayBmi);
- c.add(p, BorderLayout.CENTER);
- c.add(go, BorderLayout.SOUTH);
- }
+ Container c = getContentPane();
+ c.setBackground(Color.white);
+ JPanel panel = new JPanel();
+ panel.setLayout(new GridLayout(3, 2, 5, 5));
+ panel.add(labelLbs);
+ panel.add(massInputField);
+ panel.add(labelInches);
+ panel.add(heightInputField);
+ panel.add(labelBmi);
+ panel.add(bmiDisplayField);
+ c.add(panel, BorderLayout.CENTER);
+ c.add(go, BorderLayout.SOUTH);
+ }
- public void actionPerformed(ActionEvent e)
- {
- int lbs = Integer.parseInt(inputLbs.getText());
- int inches = Integer.parseInt(inputInches.getText());
- double bmi = calculateBmi(lbs, inches);
- DecimalFormat df = new DecimalFormat("00.0");
- displayBmi.setText(df.format(bmi));
- }
+ /**
+ * Called when the "Compute" button is clicked.
+ * @throws NumberFormatException when non-integers are entered into the height and mass input fields. Input
+ * verification should be used to mitigate this.
+ */
+ @Override
+ public void actionPerformed(ActionEvent e) {
+ int pounds = Integer.parseInt(massInputField.getText());
+ int inches = Integer.parseInt(heightInputField.getText());
+ double bmi = calculateBmi(pounds, inches);
+ DecimalFormat df = new DecimalFormat("00.0");
+ bmiDisplayField.setText(df.format(bmi));
+ }
- // Returns BMI equal to weight in kilograms divided
- // over squared height in meters.
- private double calculateBmi(int lbs, int inches)
- {
- double kg, meters;
- kg = lbs * 0.454;
- meters = inches * 0.0254;
- return kg/(meters * meters);
- }
+ /**
+ * Calculates body mass index.
+ * @param pounds mass in pounds.
+ * @param inches height in inches.
+ * @return BMI in kilograms per square meter.
+ */
+ private double calculateBmi(int pounds, int inches) {
+ double kilograms = pounds * 0.454;
+ double meters = inches * 0.0254;
+ return kilograms / Math.pow(meters, 2);
+ }
- public static void main(String[] args)
- {
- Bmi w = new Bmi();
- w.setBounds(300, 300, 300, 160);
- w.setDefaultCloseOperation(EXIT_ON_CLOSE);
- w.setVisible(true);
- }
+ public static void main(String[] args) {
+ Bmi w = new Bmi();
+ w.setBounds(300, 300, 300, 160);
+ w.setDefaultCloseOperation(EXIT_ON_CLOSE);
+ w.setVisible(true);
+ }
}
\ No newline at end of file
diff --git a/src/main/java/chapter06/dogyears/DogYearsConverter.java b/src/main/java/chapter06/dogyears/DogYearsConverter.java
new file mode 100644
index 0000000..402ce91
--- /dev/null
+++ b/src/main/java/chapter06/dogyears/DogYearsConverter.java
@@ -0,0 +1,30 @@
+// Code written as part of the Java-Methods-Program-AP-Comp-A-2021-2022 repository on GitHub.
+package chapter06.dogyears;
+
+import java.lang.Math;
+
+/**
+ * A class that provides a method to convert dog years to human years.
+ */
+public class DogYearsConverter {
+ private static final double DOG_TO_HUMAN_YEAR_RATE = 5.3333333333;
+
+ /**
+ * Converts the given age in dog years to the equivalent age in human years.
+ * @param dogYears an age in dog years.
+ * @return the age in human years. If zero or a negative integer was passed, this returns zero.
+ */
+ public static int convertToHumanAge(int dogYears) {
+ double dogAge = 0;
+
+ if (dogYears > 0) {
+ dogAge += 13;
+ dogAge += DOG_TO_HUMAN_YEAR_RATE * (dogYears - 1);
+ }
+ return (int) Math.round(dogAge);
+ }
+
+ public static void main(String[] args) {
+ System.out.println("The dog's age is: " + convertToHumanAge(3));
+ }
+}
\ No newline at end of file
diff --git a/src/main/java/chapter06/dogyears/TheProgram.java b/src/main/java/chapter06/dogyears/TheProgram.java
deleted file mode 100644
index 87fa23e..0000000
--- a/src/main/java/chapter06/dogyears/TheProgram.java
+++ /dev/null
@@ -1,24 +0,0 @@
-package chapter06.dogyears;// Code written as part of the Java-Methods-Program-AP-Comp-A-2021-2022 repository on GitHub.
-import java.lang.Math;
-
-public class TheProgram {
-
- public static void main(String[] args)
- {
-
- System.out.println("The dog's age is: " + convertToHumanAge(3));
- }
-
- public static int convertToHumanAge (int dogYears)
- {
- double dogAge = 0;
- final double POST = 5.3333333333;
-
- if (dogYears > 0)
- {
- dogAge += 13;
- dogAge += (POST * (dogYears - 1));
- }
- return (int) Math.round(dogAge);
- }
-}
\ No newline at end of file
diff --git a/src/main/java/chapter06/piechart/Poll.java b/src/main/java/chapter06/piechart/Poll.java
index aca0c83..7fd9239 100644
--- a/src/main/java/chapter06/piechart/Poll.java
+++ b/src/main/java/chapter06/piechart/Poll.java
@@ -1,28 +1,28 @@
-package chapter06.piechart;// Code written as part of the Java-Methods-Program-AP-Comp-A-2021-2022 repository on GitHub.
+// Code written as part of the Java-Methods-Program-AP-Comp-A-2021-2022 repository on GitHub.
+package chapter06.piechart;
+
import java.awt.*;
import javax.swing.*;
-public class Poll extends JFrame
-{
- public Poll()
- {
-
- super("Vote for Tami, Brian, or Liz");
+/**
+ * A {@link JFrame} window that
+ */
+public class Poll extends JFrame {
+ public Poll() {
+ super("Vote for Tami, Brian, or Liz");
- Container c = getContentPane();
- c.setBackground(Color.WHITE);
- PollDisplayPanel chart = new PollDisplayPanel("Tami", "Brian", "Liz");
- PollControlPanel controls = new PollControlPanel(chart);
- c.add(chart, BorderLayout.CENTER);
- c.add(controls, BorderLayout.SOUTH);
- }
+ Container c = getContentPane();
+ c.setBackground(Color.WHITE);
+ PollDisplayPanel chart = new PollDisplayPanel("Tami", "Brian", "Liz");
+ PollControlPanel controls = new PollControlPanel(chart);
+ c.add(chart, BorderLayout.CENTER);
+ c.add(controls, BorderLayout.SOUTH);
+ }
- public static void main(String[] args)
- {
-
- Poll w = new Poll();
- w.setBounds(300, 300, 400, 400);
- w.setDefaultCloseOperation(EXIT_ON_CLOSE);
- w.setVisible(true);
- }
+ public static void main(String[] args) {
+ Poll w = new Poll();
+ w.setBounds(300, 300, 400, 400);
+ w.setDefaultCloseOperation(EXIT_ON_CLOSE);
+ w.setVisible(true);
+ }
}
\ No newline at end of file
diff --git a/src/main/java/chapter06/piechart/PollControlPanel.java b/src/main/java/chapter06/piechart/PollControlPanel.java
index 7ccd3b2..d4207db 100644
--- a/src/main/java/chapter06/piechart/PollControlPanel.java
+++ b/src/main/java/chapter06/piechart/PollControlPanel.java
@@ -1,56 +1,52 @@
-package chapter06.piechart;// Code written as part of the Java-Methods-Program-AP-Comp-A-2021-2022 repository on GitHub.
+// Code written as part of the Java-Methods-Program-AP-Comp-A-2021-2022 repository on GitHub.
+package chapter06.piechart;
-/*
- * Implements the control panel for the chapter06.piechart.Poll program
- */
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
-public class PollControlPanel extends JPanel
- implements ActionListener
-{
- private JButton button1, button2, button3;
- private PollDisplayPanel chartPanel;
-
- public PollControlPanel(PollDisplayPanel chart)
- {
- chartPanel = chart;
-
- button1 = new JButton("Tami");
- button1.setPreferredSize(new Dimension(80, 30));
- button1.setToolTipText("Vote for Tami");
- button1.addActionListener(this);
-
- button2 = new JButton("Brian");
- button2.setPreferredSize(new Dimension(80, 30));
- button2.setToolTipText("Vote for Brian");
- button2.addActionListener(this);
-
- button3 = new JButton("Liz");
- button3.setPreferredSize(new Dimension(80, 30));
- button3.setToolTipText("Vote for Liz");
- button3.addActionListener(this);
-
- add(button1);
- add(button2);
- add(button3);
- }
-
- /**
- * Processes button events
- */
- public void actionPerformed(ActionEvent e)
- {
- JButton button = (JButton)e.getSource();
-
- if (button == button1)
- chartPanel.vote1();
- else if (button == button2)
- chartPanel.vote2();
- else if (button == button3)
- chartPanel.vote3();
- chartPanel.repaint();
- }
-
+/**
+ * Implements the control panel for the {@link chapter06.piechart.Poll} program.
+ */
+public class PollControlPanel extends JPanel implements ActionListener {
+ private JButton button1;
+ private JButton button2;
+ private JButton button3;
+ private PollDisplayPanel chartPanel;
+
+ public PollControlPanel(PollDisplayPanel chart) {
+ chartPanel = chart;
+
+ button1 = new JButton("Tami");
+ button1.setPreferredSize(new Dimension(80, 30));
+ button1.setToolTipText("Vote for Tami");
+ button1.addActionListener(this);
+
+ button2 = new JButton("Brian");
+ button2.setPreferredSize(new Dimension(80, 30));
+ button2.setToolTipText("Vote for Brian");
+ button2.addActionListener(this);
+
+ button3 = new JButton("Liz");
+ button3.setPreferredSize(new Dimension(80, 30));
+ button3.setToolTipText("Vote for Liz");
+ button3.addActionListener(this);
+
+ add(button1);
+ add(button2);
+ add(button3);
+ }
+
+ public void actionPerformed(ActionEvent e) {
+ JButton button = (JButton) e.getSource();
+
+ if (button == button1) {
+ chartPanel.vote1();
+ } else if (button == button2) {
+ chartPanel.vote2();
+ } else if (button == button3) {
+ chartPanel.vote3();
+ }
+ chartPanel.repaint();
+ }
}
\ No newline at end of file
diff --git a/src/main/java/chapter06/piechart/PollDisplayPanel.java b/src/main/java/chapter06/piechart/PollDisplayPanel.java
index c813dd7..ddd4022 100644
--- a/src/main/java/chapter06/piechart/PollDisplayPanel.java
+++ b/src/main/java/chapter06/piechart/PollDisplayPanel.java
@@ -1,150 +1,158 @@
-package chapter06.piechart;// Code written as part of the Java-Methods-Program-AP-Comp-A-2021-2022 repository on GitHub.
+// Code written as part of the Java-Methods-Program-AP-Comp-A-2021-2022 repository on GitHub.
+package chapter06.piechart;
+
+import javax.swing.*;
+import java.awt.*;
+
/**
- * A chapter06.piechart.PollDisplayPanel holds the vote counts and
- * displays the numbers and the pie chart for
- * the current vote counts.
+ * A class that holds the vote counts and displays the numbers and the pie chart for them.
*/
+public class PollDisplayPanel extends JPanel {
+ private String name1;
+ private String name2;
+ private String name3;
+ private int count1;
+ private int count2;
+ private int count3;
+
+ public PollDisplayPanel(String name1, String name2, String name3) {
+ setBackground(Color.WHITE);
+ this.name1 = name1;
+ this.name2 = name2;
+ this.name3 = name3;
+ count1 = 0; // These are optional as Java automatically initializes class properties to reasonable defaults
+ count2 = 0; // (e.g., int to 0, float to 0.0f, any Object to null). However, it is considered bad style to
+ count3 = 0; // rely on this. https://docs.oracle.com/javase/tutorial/java/nutsandbolts/datatypes.html
+ }
+
+ public void vote1() {
+ count1++;
+ }
+
+ public void vote2() {
+ count2++;
+ }
+
+ public void vote3() {
+ count3++;
+ }
-import java.awt.Color;
-import java.awt.Graphics;
-import javax.swing.JPanel;
-import java.math.*;
-
-public class PollDisplayPanel extends JPanel
-{
- private String name1, name2, name3;
- // Declare the int fields count1, count2, count3:
- private int count1, count2, count3;
-
- // Constructor
- public PollDisplayPanel(String nm1, String nm2, String nm3)
- {
- setBackground(Color.WHITE);
- name1 = nm1;
- name2 = nm2;
- name3 = nm3;
- count1 = 0; // optional
- count2 = 0; // optional
- count3 = 0; // optional
- }
-
- // Increments count1
- public void vote1()
- {
- count1++;
- }
-
- // Increments count2
- public void vote2()
- {
- count2++;
- }
-
- // Increments count3
- public void vote3()
- {
- count3++;
- }
-
- // Returns a string representation of this object
- public String toString()
- {
- return ("Tami: " + count1 + " Brian: " + count2 + " Liz: " + count3);
- }
-
- // Redefines JPanel's paintComponent to draw this pie chart
- public void paintComponent(Graphics g)
- {
- super.paintComponent(g);
-
- int w = getWidth();
- int h = getHeight();
- int x = w/2;
- int y = h/2;
- int r = Math.min(w, h) / 4;
- drawPieChart(g, x, y, r);
- drawLegend(g, x, y, r);
- }
-
- // Draws the pie chart.
- // To avoid gaps in the picture, the following algorithm is used:
- // 1. set fromDegree to 0;
- // 2. draw the red sector and increment fromDegree by its size
- // 3. draw the green sector and increment fromDegree by its size
- // 4. set the size of the blue sector to the remaining
- // area, 360 - fromDegree, but not less than 0:
- // degrees = Math.max(360 - fromDegree, 0);
- // (Occasionally, due to rounding errors, fromDegree may become 361,
- // for example, count1 = 5, count2 = 11, count3 = 0.)
- private void drawPieChart(Graphics g, int x, int y, int r)
- {
- int total = count1 + count2 + count3;
- int fromDegree = 0;
-
- if (total > 0)
- {
- int degrees;
- g.setColor(Color.RED);
- degrees = countToDegrees(count1, total);
- drawSector(g, x, y, r, fromDegree, degrees);
- fromDegree += degrees;
-
- g.setColor(Color.GREEN);
- degrees = countToDegrees(count2, total);
- drawSector(g, x, y, r, fromDegree, degrees);
- fromDegree += degrees;
-
- g.setColor(Color.BLUE);
- degrees = Math.max(360 - fromDegree, 0);
- drawSector(g, x, y, r, fromDegree, degrees);
+ @Override
+ public String toString() {
+ return (name1 + ": " + count1 + ", " + name2 + ": " + count2 + ", " + name3 + ": " + count3);
}
- else
- {
- g.setColor(Color.LIGHT_GRAY);
- drawSector(g, x, y, r, fromDegree, 360);
+
+ /**
+ * Overrides the {@link JPanel#paintComponent(Graphics) paintComponent()} method in {@link JPanel} to
+ * draw a pie chart.
+ */
+ @Override
+ public void paintComponent(Graphics g) {
+ super.paintComponent(g);
+
+ int width = getWidth();
+ int height = getHeight();
+ int x = width / 2;
+ int y = height / 2;
+ int radius = Math.min(width, height) / 4;
+ drawPieChart(g, x, y, radius);
+ drawLegend(g, x, y, radius);
+ }
+
+ /**
+ * Draws a pie chart.
+ *
+ * To avoid gaps in the picture, the following algorithm is used:
+ *
+ * - Set {@code fromDegree} to 0.
+ * - Draw the red sector and increment {@code fromDegree} by its size.
+ * - Draw the green sector and increment {@code fromDegree} by its size.
+ * - Set the size of the blue sector to the remaining area, except if it is less than zero, at which
+ * point we set it to zero. Occasionally, due to rounding errors, {@code fromDegree} may be set to 361 if,
+ * for example, count1 = 5, count2 = 11, and count3 = 0.
+ *
+ *
+ * @param g the {@link Graphics} context to be used.
+ * @param x TODO needs description
+ * @param y TODO needs description
+ * @param radius the radius of the pie chart to be drawn.
+ */
+ private void drawPieChart(Graphics g, int x, int y, int radius) {
+ int total = count1 + count2 + count3;
+ int fromDegree = 0;
+
+ if (total > 0) {
+ int degrees;
+ g.setColor(Color.RED);
+ degrees = countToDegrees(count1, total);
+ drawSector(g, x, y, radius, fromDegree, degrees);
+ fromDegree += degrees;
+
+ g.setColor(Color.GREEN);
+ degrees = countToDegrees(count2, total);
+ drawSector(g, x, y, radius, fromDegree, degrees);
+ fromDegree += degrees;
+
+ g.setColor(Color.BLUE);
+ degrees = Math.max(360 - fromDegree, 0);
+ drawSector(g, x, y, radius, fromDegree, degrees);
+ } else {
+ g.setColor(Color.LIGHT_GRAY);
+ drawSector(g, x, y, radius, fromDegree, 360);
+ }
+ }
+
+ /**
+ * Draws a legend containing vote counts and their corresponding colored squares.
+ * @param g the {@link Graphics} context to be used.
+ * @param x TODO
+ * @param y TODO
+ * @param r TODO
+ */
+ private void drawLegend(Graphics g, int x, int y, int r) {
+ // Display the counts:
+ y += (r + 20);
+ g.setColor(Color.BLACK);
+ g.drawString(name1 + ": " + count1, x - r, y);
+ g.drawString(name2 + ": " + count2, x, y);
+ g.drawString(name3 + ": " + count3, x + r, y);
+
+ // Display the color squares:
+ y += 5;
+ x -= 2;
+ g.setColor(Color.RED);
+ g.fillRect(x - r, y, 10, 10);
+ g.setColor(Color.GREEN);
+ g.fillRect(x, y, 10, 10);
+ g.setColor(Color.BLUE);
+ g.fillRect(x + r, y, 10, 10);
+ }
+
+ /**
+ * Converts a given proportion to degrees.
+ * @param count the part of the total.
+ * @param total the total.
+ * @return the proportion in degrees.
+ */
+ private int countToDegrees(int count, int total) {
+ return (int) ((double) count / total * 360);
+ }
+
+ /**
+ * Draws a sector of a circle.
+ *
+ * @param g the {@link Graphics} context to be used.
+ * @param x the x-coordinate of the center of the circle.
+ * @param y the y-coordinate of the center of the circle.
+ * @param radius the radius of the circle.
+ * @param fromDegree the starting angle of the sector.
+ * @param degrees the size of the sector in degrees.
+ */
+ private void drawSector(Graphics g, int x, int y, int radius, int fromDegree, int degrees) {
+ if (degrees > 359) {
+ g.fillOval(x - radius, y - radius, 2 * radius, 2 * radius);
+ } else {
+ g.fillArc(x - radius, y - radius, 2 * radius, 2 * radius, fromDegree, degrees);
+ }
}
- }
-
- // Draws the vote counts and the corresponding color squares.
- private void drawLegend(Graphics g, int x, int y, int r)
- {
- // Display the counts:
- y += (r + 20);
- g.setColor(Color.BLACK);
-
- g.drawString(name1 + ": " + count1, x - r, y);
-
- g.drawString(name2 + ": " + count2, x, y);
-
- g.drawString(name3 + ": " + count3, x + r, y);
-
-
- // Display the color squares:
- y += 5;
- x -= 2;
- g.setColor(Color.RED);
- g.fillRect(x - r, y, 10, 10);
- g.setColor(Color.GREEN);
- g.fillRect(x, y, 10, 10);
- g.setColor(Color.BLUE);
- g.fillRect(x + r, y, 10, 10);
- }
-
- // Returns the number of degrees in a pie slice that
- // corresponds to count / total, rounded to the nearest integer.
- private int countToDegrees(int count, int total)
- {
- return (int) ((double) count / total * 360);
- }
-
-
- // Draws a sector, centered at x, y, of radius r,
- // of angle measure degrees, starting at fromDegree.
- private void drawSector(Graphics g, int x, int y, int r, int fromDegree, int degrees)
- {
- if (degrees > 359)
- g.fillOval(x - r, y - r, 2 * r, 2 * r);
- else
- g.fillArc(x - r, y - r, 2 * r, 2 * r, fromDegree, degrees);
- }
}
diff --git a/src/main/java/chapter06/rainbow/Rainbow.java b/src/main/java/chapter06/rainbow/Rainbow.java
index bb4809a..bb395f1 100644
--- a/src/main/java/chapter06/rainbow/Rainbow.java
+++ b/src/main/java/chapter06/rainbow/Rainbow.java
@@ -1,64 +1,58 @@
-package chapter06.rainbow;// Code written as part of the Java-Methods-Program-AP-Comp-A-2021-2022 repository on GitHub.
+// Code written as part of the Java-Methods-Program-AP-Comp-A-2021-2022 repository on GitHub.
+package chapter06.rainbow;
+
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Container;
import javax.swing.JFrame;
import javax.swing.JPanel;
-public class Rainbow extends JPanel
-{
- private final Color skyColor = Color.CYAN;
-
- public Rainbow()
- {
- setBackground(skyColor);
- }
-
- // Draws the rainbow.
- public void paintComponent(Graphics g)
- {
- super.paintComponent(g);
- int width = getWidth();
- int height = getHeight();
- int xCenter = width/2, yCenter = (3*height)/4;
-
- int largeRadius = width / 4;
- int smallRadius = height / 4;
- int mediumRadius = (int)Math.sqrt(smallRadius * largeRadius);
- int skyRadius = largeRadius - 3 * mediumRadius + 3 * smallRadius;
-
- g.setColor(Color.RED);
- g.fillArc(xCenter - largeRadius, yCenter - largeRadius, largeRadius * 2, largeRadius * 2, 0, 180);
-
- g.setColor(Color.GREEN);
- g.fillArc( xCenter - mediumRadius, yCenter - mediumRadius, mediumRadius * 2, mediumRadius * 2, 0, 180 );
-
- g.setColor(Color.MAGENTA);
- g.fillArc( xCenter - smallRadius, yCenter - smallRadius, smallRadius * 2, smallRadius * 2, 0, 180 );
-
- g.setColor(Color.CYAN);
- g.fillArc( xCenter - skyRadius, yCenter - skyRadius, skyRadius * 2, skyRadius * 2, 0, 180 );
-
- // Declare and initialize the radii of the small and medium
- // semicircles and draw them:
- // ________________________________________________
-
- // Calculate the radius of the innermost (sky-color) semicircle
- // so that the width of the middle (green) ring is the
- // arithmetic mean of the widths of the red and magenta rings:
- // ________________________________________________
-
- // Draw the sky-color semicircle:
- // ________________________________________________
- }
-
- public static void main(String[] args)
- {
- JFrame w = new JFrame("chapter06.rainbow.Rainbow");
- w.setBounds(300, 300, 300, 200);
- w.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
- Container c = w.getContentPane();
- c.add(new Rainbow());
- w.setVisible(true);
- }
+/**
+ * A {@link JPanel} with a rainbow on it.
+ */
+public class Rainbow extends JPanel {
+ private static final Color SKY_COLOR = Color.CYAN;
+
+ public Rainbow() {
+ setBackground(SKY_COLOR);
+ }
+
+ /**
+ * Overrides the {@link JPanel#paintComponent(Graphics) paintComponent()} method in {@link JPanel} to
+ * draw a rainbow.
+ */
+ @Override
+ public void paintComponent(Graphics g) {
+ super.paintComponent(g);
+ int width = getWidth();
+ int height = getHeight();
+ int xCenter = width / 2;
+ int yCenter = (3 * height) / 4;
+
+ int largeRadius = width / 4;
+ int smallRadius = height / 4;
+ int mediumRadius = (int) Math.sqrt(smallRadius * largeRadius);
+ int skyRadius = largeRadius - 3 * mediumRadius + 3 * smallRadius;
+
+ g.setColor(Color.RED);
+ g.fillArc(xCenter - largeRadius, yCenter - largeRadius, largeRadius * 2, largeRadius * 2, 0, 180);
+
+ g.setColor(Color.GREEN);
+ g.fillArc(xCenter - mediumRadius, yCenter - mediumRadius, mediumRadius * 2, mediumRadius * 2, 0, 180);
+
+ g.setColor(Color.MAGENTA);
+ g.fillArc(xCenter - smallRadius, yCenter - smallRadius, smallRadius * 2, smallRadius * 2, 0, 180);
+
+ g.setColor(Color.CYAN);
+ g.fillArc(xCenter - skyRadius, yCenter - skyRadius, skyRadius * 2, skyRadius * 2, 0, 180);
+ }
+
+ public static void main(String[] args) {
+ JFrame w = new JFrame("chapter06.rainbow.Rainbow");
+ w.setBounds(300, 300, 300, 200);
+ w.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+ Container c = w.getContentPane();
+ c.add(new Rainbow());
+ w.setVisible(true);
+ }
}
\ No newline at end of file