Source code for Calculator application implemented using java swing API

Source code for Calculator application implemented using java swing API ......

here is the code for the application ....its a mini project although a desktop application and it works well because i thoroughly tested it ...

       

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.KeyStroke;

public class Calculator extends JFrame implements ActionListener {
 final int MAX_INPUT_LENGTH = 15;
 final int INPUT_MODE = 0;
 final int RESULT_MODE = 1;
 final int ERROR_MODE = 2;
 int displayMode;

 boolean clearOnNextDigit, percent;
 double lastNumber;
 String lastOperator;

 private JMenu jmenuFile, jmenuHelp;
 private JMenuItem jmenuitemExit, jmenuitemAbout;

 private JLabel jlbOutput;
 private JButton jbnButtons[];
 private JPanel jplMaster, jplBackSpace, jplControl;

 Font f1 = new Font("Times New Roman", 0, 18);
 Font f12 = new Font("Times New Roman", 1, 18);

 public Calculator() {
  jmenuFile = new JMenu("File");
  jmenuFile.setFont(f12);
  jmenuFile.setMnemonic(KeyEvent.VK_F);

  jmenuitemExit = new JMenuItem("Exit");
  jmenuitemExit.setFont(f1);
  jmenuitemExit.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_X,
   ActionEvent.CTRL_MASK));
  jmenuFile.add(jmenuitemExit);

  jmenuHelp = new JMenu("Help");
  jmenuHelp.setFont(f12);
  jmenuHelp.setMnemonic(KeyEvent.VK_H);

  jmenuitemAbout = new JMenuItem("About Calculator");
  jmenuitemAbout.setFont(f1);
  jmenuHelp.add(jmenuitemAbout);

  JMenuBar mb = new JMenuBar();
  mb.add(jmenuFile);
  mb.add(jmenuHelp);
  setJMenuBar(mb);

  setBackground(Color.gray);

  jplMaster = new JPanel();

  jlbOutput = new JLabel("0");
  jlbOutput.setHorizontalTextPosition(JLabel.RIGHT);
  jlbOutput.setBackground(Color.WHITE);
  jlbOutput.setOpaque(true);
  getContentPane().add(jlbOutput, BorderLayout.NORTH);

  jbnButtons = new JButton[18];
  JPanel jplButtons = new JPanel();
  for (int i = 0; i <= 9; i++) {
   jbnButtons[i] = new JButton(String.valueOf(i));
  }

  jbnButtons[10] = new JButton(".");
  jbnButtons[11] = new JButton("=");
  jbnButtons[12] = new JButton("/");
  jbnButtons[13] = new JButton("*");
  jbnButtons[14] = new JButton("-");
  jbnButtons[15] = new JButton("+");

  jplBackSpace = new JPanel();
  jplBackSpace.setLayout(new GridLayout(1, 1, 2, 3));

  jbnButtons[16] = new JButton("Backspace");
  jplBackSpace.add(jbnButtons[16]);
  jplControl = new JPanel();
  jplControl.setLayout(new GridLayout(1, 2, 2, 3));

  jbnButtons[17] = new JButton("C");
  jplControl.add(jbnButtons[17]);

  for (int i = 0; i < jbnButtons.length; i++) {
   jbnButtons[i].setFont(f12);

   if (i < 10)
    jbnButtons[i].setForeground(Color.blue);

   else
    jbnButtons[i].setForeground(Color.red);
  }

  jplButtons.setLayout(new GridLayout(4, 5, 2, 4));

  for (int i = 7; i <= 9; i++) {
   jplButtons.add(jbnButtons[i]);
  }

  jplButtons.add(jbnButtons[10]);
  jplButtons.add(jbnButtons[12]);


  for (int i = 4; i <= 6; i++) {
   jplButtons.add(jbnButtons[i]);
  }

  jplButtons.add(jbnButtons[14]);
  jplButtons.add(jbnButtons[11]);



  for (int i = 1; i <= 3; i++) {
   jplButtons.add(jbnButtons[i]);
  }

  jplButtons.add(jbnButtons[0]);
  jplButtons.add(jbnButtons[13]);
  jplButtons.add(jbnButtons[15]);
  jplButtons.add(jbnButtons[16]);
  jplButtons.add(jbnButtons[17]);


  jplMaster.setLayout(new BorderLayout());
  jplMaster.add(jplBackSpace, BorderLayout.WEST);
  jplMaster.add(jplControl, BorderLayout.EAST);
  jplMaster.add(jplButtons, BorderLayout.SOUTH);

  getContentPane().add(jplMaster, BorderLayout.SOUTH);
  requestFocus();

  for (int i = 0; i < jbnButtons.length; i++) {
   jbnButtons[i].addActionListener(this);
  }

  jmenuitemAbout.addActionListener(this);
  jmenuitemExit.addActionListener(this);

  clearAll();

  addWindowListener(new WindowAdapter() {

   public void windowClosed(WindowEvent e) {
    System.exit(0);
   }
  });
  this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 }


 public void actionPerformed(ActionEvent e) {
  double result = 0;

  if (e.getSource() == jmenuitemAbout) {
   JDialog dlgAbout = new CustomABOUTDialog(this, "About Java Swing Calculator", true);
   dlgAbout.setVisible(true);
  } else if (e.getSource() == jmenuitemExit) {
   System.exit(0);
  }
  for (int i = 0; i < jbnButtons.length; i++) {
   if (e.getSource() == jbnButtons[i]) {
    switch (i) {
     case 0:
      addDigitToDisplay(i);
      break;

     case 1:
      addDigitToDisplay(i);
      break;

     case 2:
      addDigitToDisplay(i);
      break;

     case 3:
      addDigitToDisplay(i);
      break;

     case 4:
      addDigitToDisplay(i);
      break;

     case 5:
      addDigitToDisplay(i);
      break;

     case 6:
      addDigitToDisplay(i);
      break;

     case 7:
      addDigitToDisplay(i);
      break;

     case 8:
      addDigitToDisplay(i);
      break;

     case 9:
      addDigitToDisplay(i);
      break;


     case 10: // decimal point
      addDecimalPoint();
      break;

     case 11: // =
      processEquals();
      break;

     case 12: // divide
      processOperator("/");
      break;

     case 13: // *
      processOperator("*");
      break;

     case 14: // -
      processOperator("-");
      break;

     case 15: // +
      processOperator("+");
      break;



     case 16: // backspace
      if (displayMode != ERROR_MODE) {
       setDisplayString(getDisplayString().substring(0,
        getDisplayString().length() - 1));

       if (getDisplayString().length() < 1)
        setDisplayString("0");
      }
      break;


     case 17: // C
      clearAll();
      break;
    }
   }
  }
 }

 void setDisplayString(String s) {
  jlbOutput.setText(s);
 }

 String getDisplayString() {
  return jlbOutput.getText();
 }

 void addDigitToDisplay(int digit) {
  if (clearOnNextDigit)
   setDisplayString("");

  String inputString = getDisplayString();

  if (inputString.indexOf("0") == 0) {
   inputString = inputString.substring(1);
  }

  if ((!inputString.equals("0") || digit > 0) && inputString.length() < MAX_INPUT_LENGTH) {
   setDisplayString(inputString + digit);
  }


  displayMode = INPUT_MODE;
  clearOnNextDigit = false;
 }

 void addDecimalPoint() {
  displayMode = INPUT_MODE;

  if (clearOnNextDigit)
   setDisplayString("");

  String inputString = getDisplayString();
  if (inputString.indexOf(".") < 0)
   setDisplayString(new String(inputString + "."));
 }



 void clearAll() {
  setDisplayString("0");
  lastOperator = "0";
  lastNumber = 0;
  displayMode = INPUT_MODE;
  clearOnNextDigit = true;
 }



 double getNumberInDisplay() {
  String input = jlbOutput.getText();
  return Double.parseDouble(input);
 }

 void processOperator(String op) {
  if (displayMode != ERROR_MODE) {
   double numberInDisplay = getNumberInDisplay();

   if (!lastOperator.equals("0")) {
    try {
     double result = processLastOperator();
     displayResult(result);
     lastNumber = result;
    } catch (DivideByZeroException e) {}
   } else {
    lastNumber = numberInDisplay;
   }

   clearOnNextDigit = true;
   lastOperator = op;
  }
 }

 void processEquals() {
  double result = 0;

  if (displayMode != ERROR_MODE) {
   try {
    result = processLastOperator();
    displayResult(result);
   } catch (DivideByZeroException e) {
    displayError("Cannot divide by zero!");
   }

   lastOperator = "0";
  }
 }

 double processLastOperator() throws DivideByZeroException {
  double result = 0;
  double numberInDisplay = getNumberInDisplay();

  if (lastOperator.equals("/")) {
   if (numberInDisplay == 0)
    throw (new DivideByZeroException());

   result = lastNumber / numberInDisplay;
  }

  if (lastOperator.equals("*"))
   result = lastNumber * numberInDisplay;

  if (lastOperator.equals("-"))
   result = lastNumber - numberInDisplay;

  if (lastOperator.equals("+"))
   result = lastNumber + numberInDisplay;

  return result;
 }

 void displayResult(double result) {
  setDisplayString(Double.toString(result));
  lastNumber = result;
  displayMode = RESULT_MODE;
  clearOnNextDigit = true;
 }

 void displayError(String errorMessage) {
  setDisplayString(errorMessage);
  lastNumber = 0;
  displayMode = ERROR_MODE;
  clearOnNextDigit = true;
 }

 public static void main(String args[]) {
  Calculator calci = new Calculator();
  Container contentPane = calci.getContentPane();
  calci.setTitle("Java Swing Calculator");
  calci.setSize(400, 360);
  calci.pack();
  calci.setLocation(300, 290);
  calci.setVisible(true);
  calci.setResizable(false);
 }

}
class DivideByZeroException extends Exception {
 public DivideByZeroException() {
  super();
 }

 public DivideByZeroException(String s) {
  super(s);
 }
}

class CustomABOUTDialog extends JDialog implements ActionListener {
 JButton jbnOk;

 CustomABOUTDialog(JFrame parent, String title, boolean modal) {
  super(parent, title, modal);
  setBackground(Color.black);

  JPanel p1 = new JPanel(new FlowLayout(FlowLayout.CENTER));

  StringBuffer text = new StringBuffer();
  text.append("Calculator Information\n\n");
  text.append("Developer: Amita Sikarwar\n class:  B.C.A 5th sem\n Roll No:  124\n\n");
  text.append("Version: 1.0");

  JTextArea jtAreaAbout = new JTextArea(5, 16);
  jtAreaAbout.setText(text.toString());
  jtAreaAbout.setFont(new Font("Times New Roman", 1, 13));
  jtAreaAbout.setEditable(false);

  p1.add(jtAreaAbout);
  p1.setBackground(Color.red);
  getContentPane().add(p1, BorderLayout.CENTER);

  JPanel p2 = new JPanel(new FlowLayout(FlowLayout.CENTER));
  jbnOk = new JButton(" OK ");
  jbnOk.addActionListener(this);

  p2.add(jbnOk);
  getContentPane().add(p2, BorderLayout.SOUTH);

  setLocation(600, 350);
  setResizable(false);

  addWindowListener(new WindowAdapter() {
   public void windowClosing(WindowEvent e) {
    Window aboutDialog = e.getWindow();
    aboutDialog.dispose();
   }
  });

  pack();
 }

 public void actionPerformed(ActionEvent e) {
  if (e.getSource() == jbnOk) {
   this.dispose();
  }
 }

}