JAVA - Calculator

 

package calculator;

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{

// Variables

final int MAX_INPUT_LENGTH = 20;

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(String name, int style, int size)

      Creates a new Font from the specified name, style and point size.

*/

Font f12 = new Font("Times New Roman", 0, 12);

Font f121 = new Font("Times New Roman", 1, 12);

// Constructor 

public Calculator() 

{

/* Set Up the JMenuBar.

* Have Provided All JMenu's with Mnemonics

* Have Provided some JMenuItem components with Keyboard Accelerators

*/ 

jmenuFile = new JMenu("File");

jmenuFile.setFont(f121);

jmenuFile.setMnemonic(KeyEvent.VK_F);

jmenuitemExit = new JMenuItem("Exit");

jmenuitemExit.setFont(f12);

jmenuitemExit.setAccelerator(KeyStroke.getKeyStroke( KeyEvent.VK_X, 

ActionEvent.CTRL_MASK));

jmenuFile.add(jmenuitemExit);

jmenuHelp = new JMenu("Help");

jmenuHelp.setFont(f121);

jmenuHelp.setMnemonic(KeyEvent.VK_H);

jmenuitemAbout = new JMenuItem("About Calculator");

jmenuitemAbout.setFont(f12);

jmenuHelp.add(jmenuitemAbout);

JMenuBar mb = new JMenuBar();

mb.add(jmenuFile);

mb.add(jmenuHelp);

setJMenuBar(mb);

//Set frame layout manager

setBackground(Color.gray);

jplMaster = new JPanel();

jlbOutput = new JLabel("0");

jlbOutput.setHorizontalTextPosition(JLabel.RIGHT);

jlbOutput.setBackground(Color.WHITE);

jlbOutput.setOpaque(true);

// Add components to frame

getContentPane().add(jlbOutput, BorderLayout.NORTH);

jbnButtons = new JButton[23];

// GridLayout(int rows, int cols, int hgap, int vgap) 

JPanel jplButtons = new JPanel(); // container for Jbuttons

// Create numeric Jbuttons

for (int i=0; i<=9; i++)

{

// set each Jbutton label to the value of index

jbnButtons[i] = new JButton(String.valueOf(i));

}

// Create operator Jbuttons

jbnButtons[10] = new JButton("+/-");

jbnButtons[11] = new JButton(".");

jbnButtons[12] = new JButton("=");

jbnButtons[13] = new JButton("/");

jbnButtons[14] = new JButton("*");

jbnButtons[15] = new JButton("-");

jbnButtons[16] = new JButton("+");

jbnButtons[17] = new JButton("sqrt");

jbnButtons[18] = new JButton("1/x");

jbnButtons[19] = new JButton("%");

jplBackSpace = new JPanel();

jplBackSpace.setLayout(new GridLayout(1, 1, 2, 2));

jbnButtons[20] = new JButton("Backspace");

jplBackSpace.add(jbnButtons[20]);

jplControl = new JPanel();

jplControl.setLayout(new GridLayout(1, 2, 2 ,2));

jbnButtons[21] = new JButton(" CE ");

jbnButtons[22] = new JButton("C");

jplControl.add(jbnButtons[21]);

jplControl.add(jbnButtons[22]);

// Setting all Numbered JButton's to Blue. The rest to Red

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);

}

// Set panel layout manager for a 4 by 5 grid

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

//Add buttons to keypad panel starting at top left

// First row

for(int i=7; i<=9; i++) {

jplButtons.add(jbnButtons[i]);

}

// add button / and sqrt

jplButtons.add(jbnButtons[13]);

jplButtons.add(jbnButtons[17]);

// Second row

for(int i=4; i<=6; i++)

{

jplButtons.add(jbnButtons[i]);

}

// add button * and x^2

jplButtons.add(jbnButtons[14]);

jplButtons.add(jbnButtons[18]);

// Third row

for( int i=1; i<=3; i++)

{

jplButtons.add(jbnButtons[i]);

}

//adds button - and %

jplButtons.add(jbnButtons[15]);

jplButtons.add(jbnButtons[19]);

//Fourth Row

// add 0, +/-, ., +, and =

jplButtons.add(jbnButtons[0]);

jplButtons.add(jbnButtons[10]);

jplButtons.add(jbnButtons[11]);

jplButtons.add(jbnButtons[16]);

jplButtons.add(jbnButtons[12]);

jplMaster.setLayout(new BorderLayout());

jplMaster.add(jplBackSpace, BorderLayout.WEST);

jplMaster.add(jplControl, BorderLayout.EAST);

jplMaster.add(jplButtons, BorderLayout.SOUTH);

// Add components to frame

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

requestFocus();

//activate ActionListener

for (int i=0; i<jbnButtons.length; i++){

jbnButtons[i].addActionListener(this);

}

jmenuitemAbout.addActionListener(this);

jmenuitemExit.addActionListener(this);

clearAll();

//add WindowListener for closing frame and ending program

addWindowListener(new WindowAdapter() {

public void windowClosed(WindowEvent e)

{

System.exit(0);

}

}

);

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

} //End of Contructor Calculator

// Perform action

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);

}

// Search for the button pressed until end of array or key found

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: // +/-

processSignChange();

break;

case 11: // decimal point

addDecimalPoint();

break;

case 12: // =

processEquals();

break;

case 13: // divide

processOperator("/");

break;

case 14: // *

processOperator("*");

break;

case 15: // -

processOperator("-");

break;

case 16: // +

processOperator("+");

break;

case 17: // sqrt

if (displayMode != ERROR_MODE)

{

try

{

if (getDisplayString().indexOf("-") == 0)

displayError("Invalid input for function!");

result = Math.sqrt(getNumberInDisplay());

displayResult(result);

}

catch(Exception ex)

{

displayError("Invalid input for function!");

displayMode = ERROR_MODE;

}

}

break;

case 18: // 1/x

if (displayMode != ERROR_MODE){

try

{

if (getNumberInDisplay() == 0)

displayError("Cannot divide by zero!");

result = 1 / getNumberInDisplay();

displayResult(result);

}

catch(Exception ex) {

displayError("Cannot divide by zero!");

displayMode = ERROR_MODE;

}

}

break;

case 19: // %

if (displayMode != ERROR_MODE){

try {

result = getNumberInDisplay() / 100;

displayResult(result);

}

catch(Exception ex) {

displayError("Invalid input for function!");

displayMode = ERROR_MODE;

}

}

break;

case 20: // backspace

if (displayMode != ERROR_MODE){

setDisplayString(getDisplayString().substring(0,

getDisplayString().length() - 1));

if (getDisplayString().length() < 1)

setDisplayString("0");

}

break;

case 21: // CE

clearExisting();

break;

case 22: // 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 the input string already contains a decimal point, don't

//  do anything to it.

if (inputString.indexOf(".") < 0)

setDisplayString(new String(inputString + "."));

}

void processSignChange(){

if (displayMode == INPUT_MODE)

{

String input = getDisplayString();

if (input.length() > 0 && !input.equals("0"))

{

if (input.indexOf("-") == 0)

setDisplayString(input.substring(1));

else

setDisplayString("-" + input);

}

}

else if (displayMode == RESULT_MODE)

{

double numberInDisplay = getNumberInDisplay();

if (numberInDisplay != 0)

displayResult(-numberInDisplay);

}

}

void clearAll() {

setDisplayString("0");

lastOperator = "0";

lastNumber = 0;

displayMode = INPUT_MODE;

clearOnNextDigit = true;

}

void clearExisting(){

setDisplayString("0");

clearOnNextDigit = true;

displayMode = INPUT_MODE;

}

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();

// contentPane.setLayout(new BorderLayout());

calci.setTitle("Java Swing Calculator");

calci.setSize(241, 217);

calci.pack();

calci.setLocation(400, 250);

calci.setVisible(true);

calci.setResizable(false);

}

} //End of Swing Calculator Class.

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: Hemanth\n");

text.append("Version: 1.0");

JTextArea jtAreaAbout = new JTextArea(5, 21);

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(408, 270);

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();

}

}

}