Chapter 23 Exercise 16, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

23.16 (Bubble sort animation) Write a program that animates the bubble sort algorithm. Create an array that consists of 20 distinct numbers from 1 to 20 in a
random order. The array elements are displayed in a histogram, as shown in
Figure 23.20b. Clicking the Step button causes the program to perform one com-
parison in the algorithm and repaints the histogram for the new array. Color the
bar that represents the number being considered in the swap. When the algorithm is finished, display a message to inform the user. Clicking the Reset button creates a new random array for a new start.

import javax.swing.*;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.Collections;

public class Exercise16 extends JApplet {

 private static final long serialVersionUID = 1L;
 private BubbleSortPanel bubbleSortPanel = new BubbleSortPanel();
 private JButton jButton1 = new JButton("Step");
 
 public Exercise16() {
  setLayout(new BorderLayout());
  add(bubbleSortPanel, BorderLayout.CENTER);
  
  JPanel panel1 = new JPanel();  
  panel1.add(jButton1);
  JButton jButton2 = new JButton("Reset");
  panel1.add(jButton2);
  add(panel1, BorderLayout.SOUTH); 
  
  jButton1.addActionListener(new ActionListener() {   
   @Override
   public void actionPerformed(ActionEvent e) {
    bubbleSortPanel.nextStep();
   }
  });
  
  jButton2.addActionListener(new ActionListener() {   
   @Override
   public void actionPerformed(ActionEvent e) {
    bubbleSortPanel.reset();
    jButton1.setEnabled(true);
   }
  });
 }

 class BubbleSortPanel extends JPanel {
  private static final long serialVersionUID = 1L;
  private int searchSize = 20;
  private int stepPosition = -1;
  private boolean needNextPass = true;
  private boolean isCylce = false;
  private int iCycle = -1; 
  ArrayList<Integer> numbers = new ArrayList<>();
  
  public BubbleSortPanel() {
   for (int i = 1; i <= searchSize; i++) {
    numbers.add(i);
   }
   reset();
  }
  
  public void nextStep() {
   if(stepPosition == -1) {
    stepPosition = 1;
   } else {
    if(!isCylce) {
     stepPosition++;
    }
   }
   if(stepPosition >= searchSize) {
    jButton1.setEnabled(false);
    stepPosition = -1;
   } else {    
    if(!isCylce) {
     needNextPass = false;
     isCylce = true;
     iCycle = 0;
    } else if (isCylce) {
     if (numbers.get(iCycle) > numbers.get(iCycle + 1)) {
      // Swap list[i] with list[i + 1]
      int temp = numbers.get(iCycle);
      numbers.set(iCycle, numbers.get(iCycle + 1));
      numbers.set(iCycle + 1, temp);
      needNextPass = true; // Next pass still needed      
     }
     iCycle++;
     if(!(iCycle < numbers.size() - stepPosition)) {
      isCylce = false;
      //iCycle = 0;
     }
    }
    if(!isCylce) {
     if(!needNextPass) {
      jButton1.setEnabled(false);
      stepPosition = -1;
      iCycle = -1; 
     }
    }    
      
   }
   repaint();  
  }
  
  public void reset() {
   Collections.shuffle(numbers);
   stepPosition = -1;
   needNextPass = true;
   isCylce = false;
   iCycle = -1; 
   repaint();
  }
  
  @Override
  protected void paintComponent(Graphics g) {
   super.paintComponent(g);
   int numberWidth = getWidth() / (searchSize + 2);
   int numberHeight = getHeight() / (searchSize + 2);
   for (int i = 0; i < searchSize; i++) {
    g.drawRect(numberWidth * (i + 1), getHeight() - numberHeight * numbers.get(i), numberWidth, numberHeight * numbers.get(i));
    g.drawString(numbers.get(i) + "", numberWidth * (i + 1), getHeight() - numberHeight * numbers.get(i) - (int)(numberHeight * 0.5));
   }
   if((iCycle != -1)&&(iCycle < searchSize)) {
    g.fillRect(numberWidth * (iCycle + 1), getHeight() - numberHeight * numbers.get(iCycle), numberWidth, numberHeight * numbers.get(iCycle));
   }
  }

 }

 public static void main(String[] args) {
  JFrame frame = new JFrame("Exercise16");
  Exercise16 applet = new Exercise16();
  frame.add(applet);
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  frame.setSize(960, 500);
  frame.setMinimumSize(new Dimension(frame.getWidth(), frame.getHeight()));
  frame.setLocationRelativeTo(null);
  frame.setVisible(true);
 }
}