Java calculator problems. Old homework just never completed correctly

[Michael W Adams]

I wrote this code directly from the book code block after code block. For my own learning experience following and typing the code myself helps me learn the syntax of code better than any copy and paste. Anyways I found myself debugging the code because of typos on my part, which is another learning experience. I cleared all bugs and it complies fine, but when I run the calculator it does not show the buttons at all. I used import java.swing.JOptionPane; at first and found that import javax.swing.JOptionPane; is the correct import format, but is this still causing the buttons not to show. I am using TextPad, but also using NetBeans because I want to move away from TextPad, they both are running the same results.

import java.awt.*;
import java.awt.event.*;
import java.awt.datatransfer.*;
import java.text.DateFormat;
import javax.swing.JOptionPane;
import java.text.DecimalFormat;

public class Calculator extends Frame implements ActionListener
{
    private Button keys[];
    private Panel keypad;
    private TextField lcd;
    private double op1;
    private boolean first;
    private boolean foundKey;
    private boolean clearText;
    private int lastOp;
    private DecimalFormat calcPattern;

    public Calculator ()
    {
        //create an instance of the menu
        MenuBar mnuBar = new MenuBar();
        setMenuBar(mnuBar);

        //construct and populate the File menu
        Menu mnuFile = new Menu("File", true);
        mnuBar.add(mnuFile);
            MenuItem mnuFileExit = new MenuItem("Exit");
            mnuFile.add(mnuFileExit);

        //construct and populate the edit menu
        Menu mnuEdit = new Menu("Edit", true);
        mnuBar.add(mnuEdit);
            MenuItem mnuEditClear = new MenuItem("Exit");
            mnuEdit.add(mnuEditClear);
            mnuEdit.insertSeparator(1);
            MenuItem mnuEditCopy = new MenuItem("Copy");
            mnuEdit.add(mnuEditCopy);
            MenuItem mnuEditPaste = new MenuItem("Paste");
            mnuEdit.add(mnuEditPaste);

        //Construct and populate the About menu
        Menu mnuAbout = new Menu("About", true);
        mnuBar.add(mnuAbout);
        MenuItem mnuAboutCalculator = new MenuItem("About Calculator");
        mnuAbout.add(mnuAboutCalculator);

        //add the ActionListner to each menu item
        mnuFileExit.addActionListener(this);
        mnuEditClear.addActionListener(this);
        mnuEditCopy.addActionListener(this);
        mnuEditPaste.addActionListener(this);
        mnuAboutCalculator.addActionListener(this);

        //assign an ActionCommand to each menu item
        mnuFileExit.setActionCommand("Exit");
        mnuEditClear.setActionCommand("Clear");
        mnuEditCopy.setActionCommand("Copy");
        mnuEditPaste.setActionCommand("Paste");
        mnuAboutCalculator.setActionCommand("About");

        //construct components and initlize begining values
        lcd = new TextField(20);
            lcd.setEditable(false);
        keypad = new Panel();
        keys = new Button[16];
        first = true;
        op1 = 0.0;
        clearText = true;
        lastOp = 0;
        calcPattern = new DecimalFormat("########.########");

        //construct and assign captions on buttons
        for (int i=0; i<=9; i++)
            keys[i] = new Button(String.valueOf(i));

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

        //set Frame and keypad layout to grid layout
        setLayout(new BorderLayout());
        keypad.setLayout(new GridLayout(4,4,10,10));
        for (int i=7; i<=10; i++)//7,8,9 divide
            keypad.add(keys[i]);

        for (int i=4; i<=6; i++)//4,5,6
            keypad.add(keys[i]);

        keypad.add(keys[11]);//multiply

        for (int i=1; i<=3; i++)//1,2,3
            keypad.add(keys[i]);

        keypad.add(keys[12]);//subtract

        keypad.add(keys[0]);//0 key

        for (int i=15; i>=13; i--)
            keypad.add(keys[i]);//decimal point, = , add (+) keys

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

        add(lcd, BorderLayout.NORTH);
        add(lcd, BorderLayout.CENTER);

        addWindowListener(
            new WindowAdapter()
            {
                public void windowClosing(WindowEvent e)
                {
                    System.exit(0);
                }
            }
        );

    }//end window constrructor

    public void actionPerformed(ActionEvent e)
    {
        //test for menu item click
        String arg = e.getActionCommand();
        if (arg == "Exit")
            System.exit(0);

        if(arg == "Clear")
        {
            clearText = true;
            first = true;
            op1 = 0.0;
            lcd.setText("");
            lcd.requestFocus();
        }

        if (arg == "Copy")
        {
            Clipboard cb = Toolkit.getDefaultToolkit().getSystemClipboard();
            StringSelection contents = new StringSelection(lcd.getText());
            cb.setContents(contents, null);
        }

        if (arg == "Paste")
        {
            Clipboard cb = Toolkit.getDefaultToolkit().getSystemClipboard();
            Transferable content = cb.getContents(this);
            try
            {
                String s = (String)content.getTransferData(DataFlavor.stringFlavor);
                lcd.setText(calcPattern.format(Double.parseDouble(s)));
            }
            catch (Throwable exc)
            {
                lcd.setText("");
            }
        }
        if (arg == "About")
        {
            String message =
                    "Calculator Version 1.0\nOpen Software\nCopyright 2016\nMikes Rights Reserved";
            JOptionPane.showMessageDialog(null,message,"About Calculator", JOptionPane.INFORMATION_MESSAGE);
        }

        //TEST FOR THE button clicks
        foundKey = false;

        //search for the clicked key
        for (int i=0; i<keys.length && !foundKey; i++)
        {
            if (e.getSource() == keys[i])
            {
                foundKey = true;
                switch(i)
                {
                    //number and decimal points
                    case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7: case 8: case 9: case 15:
                        if(clearText)
                        {
                            lcd.setText("");
                            clearText = false;
                        }
                        lcd.setText(lcd.getText() + keys[i].getLabel());
                        break;

                        //operator buttons
                    case 10: case 11: case 12: case 13: case 14:
                        clearText = true;

                        if(first)//first operand
                        {
                            if (lcd.getText().length()==0) op1 = 0.0;
                            else op1 = Double.parseDouble(lcd.getText());

                            first = false;
                            clearText = true;
                            lastOp = i; //save last operator
                        }
                        else //second opertor
                        {
                            switch(lastOp)
                            {
                                case 10: //divide button
                                    op1 /= Double.parseDouble(lcd.getText());
                                    break;
                                case 11: //multiply button
                                    op1 *= Double.parseDouble(lcd.getText());
                                    break;
                                case 12: //minus button
                                    op1 -= Double.parseDouble(lcd.getText());
                                    break;
                                case 13: //plus button
                                    op1 +=Double.parseDouble(lcd.getText());
                                    break;
                            } //end of switch(lastOp)
                            lcd.setText(calcPattern.format(op1));
                            clearText = true;


                            if (i==14) first = true; //equal button
                            else lastOp = i; //last operator
                        } //end else
                        break;
                } //end of switch (i)
            } //end of if
        }//end of for
    }//end of action performed

    public static void main(String args[])
    {
        //set frame properties
        Calculator f = new Calculator();
        f.setTitle("Calculator Application");
        f.setBounds(200,200,300,300);
        f.setVisible(true);

        //set image properties and add to frame
        Image icon = Toolkit.getDefaultToolkit().getImage("calcImage.gif");
        f.setIconImage(icon);

    }//end of main
}//end of class

[Les Morgan]

Michael,

You need to add the line

add(keypad);

to your constructor so your keypad is part of your Frame.

Les

[Norm Radder]

Also the code needs to use the equals() method to compare Strings. not the == operator.

  if(str1.equals("A String")) {

[Michael W Adams]

Thank you Les, that definitely helped. I went back into the book and seen that I had another typo after placing you response in the Frame. Found a few more mistakes that I had to correct, good learning experience. Thanks Norm, I am going to look into your response also, as of right now it is working correctly.