November 4th, 2013

import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;

/**
   This program demonstrates how to install an action listener.
*/
public class ButtonViewer
{  
   private static final int FRAME_WIDTH = 100;
   private static final int FRAME_HEIGHT = 60;

   public static void main(String[] args)
   {  
      JFrame frame = new JFrame();
      JButton button = new JButton("Click me!");
      frame.add(button);
     
      ActionListener listener = new ClickListener();
      button.addActionListener(listener);

      frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setVisible(true);
   }
}

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

/**
   An action listener that prints a message.
*/
public class ClickListener implements ActionListener
{
   public void actionPerformed(ActionEvent event)
   {
      System.out.println("I was clicked.");
   }            
}

/**
   A bank account has a balance that can be changed by 
   deposits and withdrawals.
*/
public class BankAccount
{  
   private double balance;

   /**
      Constructs a bank account with a zero balance.
   */
   public BankAccount()
   {   
      balance = 0;
   }

   /**
      Constructs a bank account with a given balance.
      @param initialBalance the initial balance
   */
   public BankAccount(double initialBalance)
   {   
      balance = initialBalance;
   }

   /**
      Deposits money into the bank account.
      @param amount the amount to deposit
   */
   public void deposit(double amount)
   {  
      double newBalance = balance + amount;
      balance = newBalance;
   }

   /**
      Withdraws money from the bank account.
      @param amount the amount to withdraw
   */
   public void withdraw(double amount)
   {   
      double newBalance = balance - amount;
      balance = newBalance;
   }

   /**
      Gets the current balance of the bank account.
      @return the current balance
   */
   public double getBalance()
   {   
      return balance;
   }
}

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;

/**
   This program demonstrates how an action listener can access 
   a variable from a surrounding block.
*/
public class InvestmentViewer1
{  
   private static final int FRAME_WIDTH = 120;
   private static final int FRAME_HEIGHT = 60;

   private static final double INTEREST_RATE = 10;
   private static final double INITIAL_BALANCE = 1000;

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

      // The button to trigger the calculation
      JButton button = new JButton("Add Interest");
      frame.add(button);

      // The application adds interest to this bank account
      final BankAccount account = new BankAccount(INITIAL_BALANCE);
      
      class AddInterestListener implements ActionListener
      {
         public void actionPerformed(ActionEvent event)
         {
            // The listener method accesses the account variable
            // from the surrounding block
            double interest = account.getBalance() * INTEREST_RATE / 100;
            account.deposit(interest);
            System.out.println("balance: " + account.getBalance());
         }            
      }
     
      ActionListener listener = new AddInterestListener();
      button.addActionListener(listener);

      frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setVisible(true);
   }
}

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

/**
   This program displays the growth of an investment. 
*/
public class InvestmentViewer2
{  
   private static final int FRAME_WIDTH = 400;
   private static final int FRAME_HEIGHT = 100;

   private static final double INTEREST_RATE = 10;
   private static final double INITIAL_BALANCE = 1000;

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

      // The button to trigger the calculation
      JButton button = new JButton("Add Interest");

      // The application adds interest to this bank account
      final BankAccount account = new BankAccount(INITIAL_BALANCE);

      // The label for displaying the results
      final JLabel label = new JLabel("balance: " + account.getBalance());

      // The panel that holds the user interface components
      JPanel panel = new JPanel();
      panel.add(button);
      panel.add(label);      
      frame.add(panel);
  
      class AddInterestListener implements ActionListener
      {
         public void actionPerformed(ActionEvent event)
         {
            double interest = account.getBalance() * INTEREST_RATE / 100;
            account.deposit(interest);
            label.setText("balance: " + account.getBalance());
         }            
      }

      ActionListener listener = new AddInterestListener();
      button.addActionListener(listener);

      frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setVisible(true);
   }
}

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import javax.swing.JComponent;

/**
   This component displays a rectangle that can be moved. 
*/
public class RectangleComponent extends JComponent
{  
   private static final int BOX_X = 100;
   private static final int BOX_Y = 100;
   private static final int BOX_WIDTH = 20;
   private static final int BOX_HEIGHT = 30;

   private Rectangle box;

   public RectangleComponent()
   {  
      // The rectangle that the paintComponent method draws
      box = new Rectangle(BOX_X, BOX_Y, BOX_WIDTH, BOX_HEIGHT);         
   }

   public void paintComponent(Graphics g)
   {  
      Graphics2D g2 = (Graphics2D) g;

      g2.draw(box);
   }

   /**
      Moves the rectangle to the given location.
      @param x the x-position of the new location
      @param y the y-position of the new location
   */
   public void moveTo(int x, int y)
   {
      box.setLocation(x, y);
      repaint();      
   }
} 

import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;

/**
   This program displays a RectangleComponent.
*/
public class RectangleComponentViewer
{  
   private static final int FRAME_WIDTH = 300;
   private static final int FRAME_HEIGHT = 400;

   public static void main(String[] args)
   {        
      final RectangleComponent component = new RectangleComponent();

      // Add mouse press listener         

      class MousePressListener implements MouseListener
      {  
         public void mousePressed(MouseEvent event)
         {  
            int x = event.getX();
            int y = event.getY();
            component.moveTo(x, y);
         }

         // Do-nothing methods
         public void mouseReleased(MouseEvent event) {}
         public void mouseClicked(MouseEvent event) {}
         public void mouseEntered(MouseEvent event) {}
         public void mouseExited(MouseEvent event) {}
      }
         
      MouseListener listener = new MousePressListener();
      component.addMouseListener(listener);

      JFrame frame = new JFrame();
      frame.add(component);

      frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setVisible(true);
   }
} 

import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import javax.swing.JComponent;

/**
   This component displays a rectangle that can be moved. 
*/
public class RectangleComponent extends JComponent
{  
   private static final int BOX_X = 100;
   private static final int BOX_Y = 100;
   private static final int BOX_WIDTH = 20;
   private static final int BOX_HEIGHT = 30;

   private Rectangle box;

   public RectangleComponent()
   {  
      // The rectangle that the paintComponent method draws 
      box = new Rectangle(BOX_X, BOX_Y, BOX_WIDTH, BOX_HEIGHT);         
   }

   public void paintComponent(Graphics g)
   {  
      Graphics2D g2 = (Graphics2D) g;

      g2.draw(box);
   }

   /**
      Moves the rectangle by a given amount. 
      @param x the amount to move in the x-direction 
      @param y the amount to move in the y-direction 
   */
   public void moveBy(int dx, int dy)
   {
      box.translate(dx, dy);
      repaint();      
   }
}

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.Timer;

/** 	 	 	 	 	 	
   This program moves the rectangle.
*/
public class RectangleMover
{
   private static final int FRAME_WIDTH = 300;
   private static final int FRAME_HEIGHT = 400;

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

      frame.setSize(FRAME_WIDTH, FRAME_HEIGHT);
      frame.setTitle("An animated rectangle");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      final RectangleComponent component = new RectangleComponent();
      frame.add(component);

      frame.setVisible(true);
      
      class TimerListener implements ActionListener
      {
         public void actionPerformed(ActionEvent event)
         {
            component.moveBy(1, 1);
         }
      }

      ActionListener listener = new TimerListener();

      final int DELAY = 100; // Milliseconds between timer ticks
      Timer t = new Timer(DELAY, listener);
      t.start();      
   }
}

Homework: Exercise 4: Enhance the ButtonViewer program so that it prints a message “I was clicked n times!” whenever the button is clicked. The value n should be incremented with each click.