/*
Java Swing 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.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;
 
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, jmenuEdit, jmenuView, jmenuHelp;
    private JMenuItem jmenuitemExit, jmenuitemCopy, jmenuitemPaste, jmenuitemStd, 
                                            jmenuitemSci, jmenuitemDigitGrp, jmenuitemAbout;
    private JDialog dialog;
 
    private JLabel display;
    private JButton button[];
    private JPanel masterPanel;
 
    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
        jmenuFile = new JMenu("File");
        jmenuFile.setFont(f121);
 
        jmenuitemExit = new JMenuItem("Exit");
        jmenuitemExit.setFont(f12);
        jmenuFile.add(jmenuitemExit);
 
        jmenuEdit = new JMenu("Edit");
        jmenuEdit.setFont(f121);
 
        jmenuitemCopy = new JMenuItem("Copy");
        jmenuitemCopy.setFont(f12);
 
        jmenuitemPaste = new JMenuItem("Paste");
        jmenuitemPaste.setFont(f12);
        jmenuEdit.add(jmenuitemCopy);        
        jmenuEdit.add(jmenuitemPaste);
 
        jmenuView = new JMenu("View");
        jmenuView.setFont(f121);
 
        jmenuitemStd = new JMenuItem("Standard");
        jmenuitemStd.setFont(f12);
 
        jmenuitemSci = new JMenuItem("Scientific");
        jmenuitemSci.setFont(f12);
 
        jmenuitemDigitGrp = new JMenuItem("Digit Grouping");
        jmenuitemDigitGrp.setFont(f12);
        jmenuView.add(jmenuitemStd); 
        jmenuView.add(jmenuitemSci); 
        jmenuView.addSeparator(); 
        jmenuView.add(jmenuitemDigitGrp);
 
        jmenuHelp = new JMenu("Help");
        jmenuHelp.setFont(f121);
 
        jmenuitemAbout = new JMenuItem("About Calculator");
        jmenuitemAbout.setFont(f12);
        jmenuHelp.add(jmenuitemAbout);
 
        JMenuBar mb = new JMenuBar();
        mb.add(jmenuFile);
        mb.add(jmenuEdit);
        mb.add(jmenuView);
//        mb.setHelpMenu(jmenuHelp);
        setJMenuBar(mb);
 
        //Set frame layout manager
 
        setBackground(Color.gray);
 
        /*
         * Font(String name, int style, int size)
Creates a new Font from the specified name, style and point size.
         */
 
 
        //adds menubar to frame (end)
 
        masterPanel = new JPanel();
 
        display = new JLabel("0");
        display.setAlignmentX(JLabel.RIGHT);
        display.setBackground(Color.cyan);
 
        Container contentPane = getContentPane();
 
        // Add components to frame
        contentPane.add(display, BorderLayout.NORTH);
 
        button = new JButton[23];
 
        JPanel backSpace = new JPanel();
        backSpace.setLayout(new GridLayout(1, 1, 2, 2));
 
        button[20] = new JButton("Backspace");
        backSpace.add(button[20]);
 
        JPanel control = new JPanel();
        control.setLayout(new GridLayout(1, 2, 2 ,2));
 
        button[21] = new JButton(" CE ");
        button[22] = new JButton("C");
 
        control.add(button[21]);
        control.add(button[22]);
 
        JPanel keyPad = new JPanel();            // container for buttons
 
        // Create numeric buttons
        for (int i=0; i<=9; i++)
        {
            // set each button label to the value of index
            button[i] = new JButton(String.valueOf(i));
        }
 
        // Create operator buttons
        button[10] = new JButton("+/-");
        button[11] = new JButton(".");
        button[12] = new JButton("=");
        button[13] = new JButton("/");
        button[14] = new JButton("*");
        button[15] = new JButton("-");
        button[16] = new JButton("+");
        button[17] = new JButton("sqrt");
        button[18] = new JButton("1/x");
        button[19] = new JButton("%");
 
        for (int i=0; i<button.length; i++)
        {
            button[i].setFont(f12);
 
            if (i<13)
                button[i].setForeground(Color.blue);
 
            else
                button[i].setForeground(Color.red);
        }
 
        // Set panel layout manager for a 4 by 5 grid
        keyPad.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++)
        {
            //adds buttons 7,8,9 and /
            keyPad.add(button[i]);
        }
 
        // add button / and sqrt
        keyPad.add(button[13]);
        keyPad.add(button[17]);
 
        // Second row
        for(int i=4; i<=6; i++)
        {
            //adds buttons 4,5,6
            keyPad.add(button[i]);
        }
 
        // add button * and x^2
        keyPad.add(button[14]);
        keyPad.add(button[18]);
 
        // Third row
        for( int i=1; i<=3; i++)
        {
            // add buttons 1,2,3
            keyPad.add(button[i]);
        }
 
        //adds button - and %
        keyPad.add(button[15]);
        keyPad.add(button[19]);
 
        //Fourth Row
        // add 0, +/-, ., +, and =
        keyPad.add(button[0]);
        keyPad.add(button[10]);
        keyPad.add(button[11]);
        keyPad.add(button[16]);
        keyPad.add(button[12]);
 
        masterPanel.setLayout(new BorderLayout());
        masterPanel.add(backSpace, BorderLayout.WEST);
        masterPanel.add(control, BorderLayout.EAST);
        masterPanel.add(keyPad, BorderLayout.SOUTH);
 
        // Add components to frame
        contentPane.add(masterPanel, BorderLayout.SOUTH);
        requestFocus();
 
        //activate ActionListener
        for (int i=0; i<button.length; i++)
        {
            button[i].addActionListener(this);
        }
 
        jmenuitemAbout.addActionListener(this);
        jmenuitemExit.addActionListener(this);
 
        clearAll();
 
        //add WindowListener for closing frame and ending program
        addWindowListener(new WindowAdapter() 
            {
                public void windowClosing(WindowEvent e)
                {
                    Window theWindow = e.getWindow();
                    theWindow.dispose();
                }
 
                public void windowClosed(WindowEvent e)
                {
                    System.exit(0);
                }
            }
       &nbsp;);
    }
 
    // Perform action
    public void actionPerformed(ActionEvent e)
    {
        double result = 0;
 
        if(e.getSource() == jmenuitemAbout)
        {
            System.out.println("Starting About Calculator window...");
            JDialog dlg = new CustomDialog(this, "About Calculator", true);
            dlg.setVisible(true);
        }
 
        else if(e.getSource() == jmenuitemExit)
        {
            System.out.println("Quitting Calculator window...");
            System.exit(0);
        }    
 
        // Search for the button pressed until end of array or key found
        for (int i=0; i<button.length; i++)
        {
            if(e.getSource() == button[i])
            {
                switch(i)
                {
                    case 0:
                        addDigit(i);
                        break;
 
                    case 1:
                        addDigit(i);
                        break;
 
                    case 2:
                        addDigit(i);
                        break;
 
                    case 3:
                        addDigit(i);
                        break;
 
                    case 4:
                        addDigit(i);
                        break;
 
                    case 5:
                        addDigit(i);
                        break;
 
                    case 6:
                        addDigit(i);
                        break;
 
                    case 7:
                        addDigit(i);
                        break;
 
                    case 8:
                        addDigit(i);
                        break;
 
                    case 9:
                        addDigit(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)
    {
        display.setText(s);
    }
 
    String getDisplayString ()
    {
        return display.getText();
    }
 
    void addDigit(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 = display.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();
 
////                if (result == 0)
////                    setDisplayString("" + Double.parseDouble(getDisplayString()));
//                    
//                if (result == 0)
// displayResult(result);
//                
//                else
                    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");
        contentPane.setSize(241, 217);
        contentPane.setLocation(400, 250);
        contentPane.setVisible(true);
        calci.setResizable(false);
    }
 
}
 
class DivideByZeroException extends Exception
{
    public DivideByZeroException()
    {
        super();
    }
 
    public DivideByZeroException(String s)
    {
        super(s);
    }
}
 
class CustomDialog extends JDialog implements ActionListener
{
    JButton OK;
 
    CustomDialog(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:    Canh Doan\n");
        text.append("Date:        09/16/03\n");
        text.append("Version:    1.0");
 
        JTextArea aboutCalc = new JTextArea(5, 21);
        aboutCalc.setText(text.toString());
        aboutCalc.setFont(new Font("Times New Roman", 1, 16));
        aboutCalc.setEditable(false);
        aboutCalc.setBackground(Color.yellow);
 
        p1.add(aboutCalc);
        p1.setBackground(Color.red);
        add(p1, BorderLayout.CENTER);
 
        JPanel p2 = new JPanel(new FlowLayout(FlowLayout.CENTER));
        OK = new JButton(" OK ");
        OK.setFont(new Font("Times New Roman", 1, 14));
        OK.setBackground(Color.white);
        OK.setForeground(Color.blue);
        OK.addActionListener(this);
 
        p2.add(OK);
        p2.setBackground(Color.blue);
        add(p2, BorderLayout.SOUTH);
 
        setLocation(408, 270);
        setResizable(false);
 
        addWindowListener(new WindowAdapter() 
            {
                public void windowClosing(WindowEvent e)
                {
                    Window aboutDialog = e.getWindow();
                    aboutDialog.dispose();
                }
            }
       &nbsp;);
 
        pack();
    }
 
    public void actionPerformed(ActionEvent e)
    {
        if(e.getSource() == OK)
        {
            System.out.println("Quitting About Calculator window...");
            this.dispose();
        }
    }
 
}