Results 1 to 3 of 3
  1. #1
    peterhabe is offline Member
    Join Date
    Jul 2010
    Rep Power

    Default Problem with if statement in a calculator program

    I'm trying to write a calculator program but i can't get if statement in the inner class, which is supposed to find out which button was clicked, to work.

    Also, would it be better to use a seperate anonymous inner class for each button to handle its events or just one inner class to handle all ActionListener events and a giant if else statement to find the button which was clicked (which is what i'm trying to do at the moment)?

    Here's a little runnable program which demonstrates my problem:

    Java Code:
    import java.awt.*;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    import javax.swing.*;
    public class CalculatorJFrame extends JFrame{
    	//Class objects
    	private ActionListenerClass actionListener = new ActionListenerClass();
    	private JPanel primaryDisplayJPanel = new JPanel();
    	private JPanel buttonsJPanel = new JPanel();
    	private JButton one, two, three, four, five, six, seven, eight, nine, zero, dot, multiply, divide, add, minus, equals, canel, clear, posNeg;
    	public CalculatorJFrame(){
    		//setting JFrame
    		setSize(240, 280);
    		//setting layout of JFrame
    		primaryDisplayJPanel.setPreferredSize(new Dimension(getWidth(), 70));
    		add(primaryDisplayJPanel, BorderLayout.NORTH);
    		add(buttonsJPanel, BorderLayout.CENTER);
    		//setting buttons
    		setButton(canel, "C", new Dimension(50, 30));
    		setButton(clear, "CE", new Dimension(50, 30));
    		setButton(posNeg, "+/-", new Dimension(50, 30));
    		setButton(divide, "/", new Dimension(50, 30));
    		setButton(one, "1", new Dimension(50, 30));
    		setButton(two, "2", new Dimension(50, 30));
    		setButton(three, "3", new Dimension(50, 30));
    		setButton(multiply, "*", new Dimension(50, 30));
    		setButton(four, "4", new Dimension(50, 30));
    		setButton(five, "5", new Dimension(50, 30));
    		setButton(six, "6", new Dimension(50, 30));
    		setButton(minus, "-", new Dimension(50, 30));
    		setButton(seven, "7", new Dimension(50, 30));
    		setButton(eight, "8", new Dimension(50, 30));
    		setButton(nine, "9", new Dimension(50, 30));
    		setButton(add, "+", new Dimension(50, 30));
    		setButton(zero, "0", new Dimension(50, 30));
    		setButton(dot, ".", new Dimension(50, 30));
    		setButton(equals, "=", new Dimension(105, 30));
    	public static void main(String args[]){
    		new CalculatorJFrame();
    	private void setButton(JButton button, String tag, Dimension dimension){
    		button = new JButton(tag);
    	private class ActionListenerClass implements ActionListener{
    		public void actionPerformed(ActionEvent event) {
    Last edited by peterhabe; 08-26-2011 at 04:30 PM.

  2. #2
    KevinWorkman's Avatar
    KevinWorkman is offline Crazy Cat Lady
    Join Date
    Oct 2010
    Washington, DC
    Rep Power


    You aren't actually setting the one reference in your setButton method. You're just replacing the reference you pass in (which is null) with a new JButton. That doesn't change the variable you passed in. Add this to your ActionListener to prove it:

    System.out.println("Null: " + (one == null));

    It's sorta like this:

    Java Code:
    public void doMath(int i){
       i = 7;
    int x = 4;
    //what is x now? It's still 4, of course!
    How to Ask Questions the Smart Way
    Static Void Games - GameDev tutorials, free Java and JavaScript hosting!
    Static Void Games forum - Come say hello!

  3. #3
    peterhabe is offline Member
    Join Date
    Jul 2010
    Rep Power

Similar Threads

  1. Getting Backspace on a java calculator program to work
    By marylanddem in forum New To Java
    Replies: 1
    Last Post: 12-09-2010, 02:01 AM
  2. Calculator program
    By kevzspeare in forum New To Java
    Replies: 6
    Last Post: 03-18-2009, 02:43 PM
  3. Calculator Program HELP NEEDED FAST! Homework assignment
    By SteroidalPsycho in forum New To Java
    Replies: 3
    Last Post: 03-05-2009, 05:02 AM
  4. unreachable statement - Java calculator program
    By V2001Gordon in forum New To Java
    Replies: 3
    Last Post: 12-13-2008, 01:57 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts