Creating a calculator

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Thread: Creating a calculator

  1. #1
    Join Date
    May 2005

    Creating a calculator

    I need help incorporating the buttons, when the user clicks the button, it should display in the textfield. How do I do this? I am using GUI. Any help would be appreciated. Here is the code:

    import TerminalIO.KeyboardReader;
    import javax.swing.*;
    import BreezySwing.*;

    public class Calculator extends GBFrame {

    // declare variables for the window objects
    private DoubleField ansField;
    private JButton oneButton;
    private JButton twoButton;
    private JButton threeButton;
    private JButton fouButton;
    private JButton fivButton;
    private JButton sixButton;
    private JButton sevButton;
    private JButton eigButton;
    private JButton ninButton;
    private JButton zerButton;
    private JButton addiButton;
    private JButton subButton;
    private JButton mulButton;
    private JButton divButton;
    private JButton dotButton;

    // Constructor
    public Calculator(){

    // Instantiate and add window objects to the window
    ansField = addDoubleField (0, 1,1,4,1);

    oneButton = addButton ("1", 4,1,1,1);
    twoButton = addButton ("2", 4,2,1,1);
    threeButton = addButton ("3", 4,3,1,1);
    fouButton = addButton ("4", 3,1,1,1);
    fivButton = addButton ("5", 3,2,1,1);
    sixButton = addButton ("6", 3,3,1,1);
    sevButton = addButton ("7", 2,1,1,1);
    eigButton = addButton ("8", 2,2,1,1);
    ninButton = addButton ("9", 2,3,1,1);
    zerButton = addButton ("0", 5,3,1,1);
    addiButton = addButton ("+", 2,4,1,1);
    subButton = addButton ("-", 3,4,1,1);
    mulButton = addButton ("*", 4,4,1,1);
    divButton = addButton ("/", 5,4,1,1);
    dotButton = addButton (".", 5,2,1,1);

    Respond to button click events
    public void buttonClicked (JButton buttonObj){
    // Local variables
    Calculator calculate = new Calculator();

    // Determine which button was clicked
    if (buttonObj == addButton){


    // Execution begins in the method main as asual.
    public static void main (String [] args) {
    Calculator theGUI = new Calculator();
    theGUI.setSize (250, 250);
    theGUI.setVisible (true);


  2. #2
    Join Date
    Nov 2004
    First of all, the instatiation of a new Calculator class inside a buttonClicked
    method seems a bit awkward to me, but it may be ok (I haven't seen its implementation).

    When one of the buttons are clicked you have three choices:

    1: add a new number char or decimal point to the display
    2: perform stacking (user enters an operator after some digits input)
    3: calculate (user enters an operator after some digits input when there is already a stacked value).

    For ease of logics you should add a "change sign" button too. Also you should not
    try to give sane responses to any "ape-iput"; don't do anything.

    To catch the button clicks you must implement the ActionListener interface
    (obviously ?) and add your class to the buttons list of actionlisteners.

    On each buttonclick that is a number char you should copy/append the
    displayfield value (after sanity checks of course):

    String dispVal=displayField.getText().trim()+charClicked;

    But if you have implemented an editable displayField you have
    quite a different ballgame to tackle
    eschew obfuscation

  3. #3
    Join Date
    May 2005


    Thank you for your opinion. I am newb at Java, and don't know how to implement all the suggestions you made. Can you please help me?

    1st: How do I make an editable text display?
    2nd: Actionlistener, how do I implement this?

  4. #4
    Join Date
    Nov 2004
    JTextField aTextField=new JTextField();
    aTextField.setEditable(true); // not required, is editable by default
    You make yourself an object (panel/frame/whatever) and implement the ActionListener
    interface for it. Then you add this object to the textcomponents' list of listeners
    aTextField.addActionListener(aListener); // aListener=any java object instance

    check this:

    ref: google
    eschew obfuscation

  5. #5
    Join Date
    May 2005
    Thank you, sjalle. This helps a lot. If I have any more questions, I'll post here. Once again, I appreciate it.

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