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 Calculadora 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 jmenuSair, jmenuAjuda;
	private JMenuItem jmenuitemExit, jmenuitemAbout;
	private JLabel jlbOutput;
	private JButton jbnButtons[];
	private JPanel jplMaster, jplBackSpace, jplControl;
	
	Font f12 = new Font("Times New Roman", 0, 12);
	Font f121 = new Font("Times New Roman", 1, 12);
	// Constructor
	public Calculadora() {
	
		jmenuFile = new JMenu("Arquivo");
		jmenuFile.setFont(f121);
		jmenuFile.setMnemonic(KeyEvent.VK_F);
		jmenuitemSair = new JMenuItem("Sair");
		jmenuitemSair.setFont(f12);
		jmenuitemSair.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_X,
				ActionEvent.CTRL_MASK));
		jmenuFile.add(jmenuitemExit);
		jmenuAjuda = new JMenu("Ajuda");
		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 &lt; jbnButtons.length; i++) {
			jbnButtons[i].setFont(f12);
			if (i &lt; 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 &lt;= 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 &lt;= 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 &lt;= 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 &lt; 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);
			}
		});
	} //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&lt; 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 &gt; 0)
				&amp;&amp; inputString.length() &lt; 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(".") &lt; 0)
			setDisplayString(new String(inputString + "."));
	}
	void processSignChange() {
		if (displayMode == INPUT_MODE) {
			String input = getDisplayString();
			if (input.length() &gt; 0 &amp;&amp; !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[]) {
		Calculadora calci = new Calculadora();
		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();
		}
	}
}