Chapter 23 Exercise 17, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

23.17 (Radix sort animation) Write a program that animates the radix sort algorithm. Create an array that consists of 20 random numbers from 0 to 1,000. The array elements are displayed, as shown in Figure  23.21. Clicking the Step button causes the program to place a number in a bucket. The number that has just been placed is displayed in red. Once all the numbers are placed in the buckets, clicking the Step button collects all the numbers from the buckets and moves them back to the array. When the algorithm is finished, clicking the Step button displays 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;

public class Exercise17 extends JApplet {

 private static final long serialVersionUID = 1L;
 private RadixSortPanel radixSortPanel = new RadixSortPanel();
 private JButton jButton1 = new JButton("Step");
 
 public Exercise17() {
  setLayout(new BorderLayout());
  add(radixSortPanel, 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) {
    radixSortPanel.nextStep();
   }
  });
  
  jButton2.addActionListener(new ActionListener() {   
   @Override
   public void actionPerformed(ActionEvent e) {
    radixSortPanel.reset();
    jButton1.setEnabled(true);
   }
  });
 }
 

 class RadixSortPanel extends JPanel {
  private static final long serialVersionUID = 1L;
  private int searchSize = 30;
  private int maxOrder = 1000;
  private int order = 1;
  private boolean isCycle = false;
  private int iCycle = 0;
  private ArrayList<Integer>[] bucket;
  int lastNumberCol = 0;
  ArrayList<Integer> numbers = new ArrayList<>();
  
  public RadixSortPanel() {
   reset();
  }
  
  @SuppressWarnings("unchecked")
  public void nextStep() {
   if(!isCycle) {
    bucket = new ArrayList[10];
    for (int i = 0; i < bucket.length; i++) {
     bucket[i] = new java.util.ArrayList<>();
    }
    isCycle = true;
    iCycle = 0;
   }
   
   if(isCycle) {
    bucket[(numbers.get(iCycle) / order) % 10].add(numbers.get(iCycle));
    lastNumberCol = (numbers.get(iCycle) / order) % 10;
    iCycle++;
    if(iCycle >= numbers.size()) {
     isCycle = false;
    }
   }
   
   if(!isCycle) {
    int k = 0;
    for (int i = 0; i < bucket.length; i++) {
     if (bucket[i] != null) {
      for (int j = 0; j < bucket[i].size(); j++)
       numbers.set(k++, bucket[i].get(j));
     }
    }
    order *= 10;
    if(order >= maxOrder) {
     jButton1.setEnabled(false);
     order = 1;
    }
    bucket = null;
   }
   repaint();  
  }
  
  public void reset() {
   numbers.clear();
   for (int i = 1; i <= searchSize; i++) {
    numbers.add((int)(Math.random() * maxOrder));
   }
   order = 1;
   isCycle = false;
   iCycle = 0;
   bucket = null;
   lastNumberCol = 0;
   repaint();
  }
  
  @Override
  protected void paintComponent(Graphics g) {
   super.paintComponent(g);
   int numberWidth = getWidth() / (searchSize + 2);
   int numberHeight = 20;
   for (int i = 0; i < searchSize; i++) {
    g.drawRect(numberWidth * (i + 1), 20, numberWidth, numberHeight);
    g.drawString(numbers.get(i) + "", numberWidth * (i + 1) + 5, 35);
   }
   
   int columns = 10;
   int columnWidth = getWidth() / columns;
   int columnHeight = getHeight() - 80;
   for (int i = 0; i < columns; i++) {
    g.drawRect(columnWidth * i + 10, 60, columnWidth - 20, columnHeight);
    if(bucket != null) {
    for (int j = 0; j < bucket[i].size(); j++) {
     if((i == lastNumberCol)&&(j == bucket[i].size() - 1)) {
      g.setColor(Color.RED);
     }
     g.drawString(bucket[i].get(j) + "", columnWidth * i + 20, 90 + j * 20);
     if((i == lastNumberCol)&&(j == bucket[i].size() - 1)) {
      g.setColor(Color.BLACK);
     }
    }
    }
   }
  }

 }

 public static void main(String[] args) {
  JFrame frame = new JFrame("Exercise17");
  Exercise17 applet = new Exercise17();
  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);
 }
}