Java: Roller program - debug - variables not updating from JTextField and NumberFormatException thrown regardless of valid information

Question

Problems: I am unable to get the values of the JTextFields or the rollResultTotal to update. Even if the data in the JTextFields are valid, a NumberFormatException is still thrown.

Questions: Why don't the variables stay? Is this due to declaration in the class itself? Is it possible to update a JLabel panel to show an updated result? (tried this, epic failure)

Thanks in advance for any input and examples.

/*
   ITP-120:     Final Project
   Programmer:  S. Schnoor
   Date:        November 7th, 2009
   Filename:    SchnoorProject.java
   Purpose:     To generate "dice rolls" - a tally of random values as defined by the user,
                including a final calculation modifier.
*/

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import java.lang.*;
import java.math.*;

public class SchnoorProject extends JFrame implements ActionListener, EventListener
{
    // Declare Class Variables
    int sidesToRoll, diceToRoll, diceLeft, modifier, rollResult, rollResultTotal;
    String getSides, getDice, getModifier;
    JTextField inputSides       = new JTextField();
    JTextField inputDice        = new JTextField();
    JTextField inputModifier    = new JTextField();
    Random roll;

    // Panels and Buttons
    JPanel rollPanel;
    JButton newRollButton, helpButton, exitButton;

    // Create Colors
    Color darkPurple        = new Color ( 80,   0,  80);
    Color darkGold          = new Color (255, 215,   0);
    Color darkCoal          = new Color ( 24,  24,  24);
    Color crimson           = new Color (127,  12,  12);
    Color ltSilver          = new Color (140, 140, 180);

    public static void main(String args[])
    {
        JFrame frame = new SchnoorProject();

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

    frame.addWindowListener(l);
    frame.pack();
    frame.setVisible(true);

    }

    public SchnoorProject()
    {
        // Construction of Components
        rollPanel                           = new JPanel();
        getContentPane().add(rollPanel);


        JLabel      sidesLabel              = new JLabel ("Enter the number of sides on each die below.  (1 to 99)");
                    sidesLabel.setForeground(darkGold);
                    sidesLabel.setHorizontalAlignment(sidesLabel.CENTER);

        JTextField  inputSides              = new JTextField("6");
                    inputSides.setBackground(darkCoal);
                    inputSides.setForeground(darkGold);
                    inputSides.setHorizontalAlignment(inputSides.CENTER);

        JLabel      diceLabel               = new JLabel ("Enter the number of dice to roll below.  (1 to 99)");
                    diceLabel.setForeground(darkGold);
                    diceLabel.setHorizontalAlignment(diceLabel.CENTER);

        JTextField  inputDice               = new JTextField("3");
                    inputDice.setBackground(darkCoal);
                    inputDice.setForeground(darkGold);
                    inputDice.setHorizontalAlignment(inputDice.CENTER);

        JLabel      modifierLabel           = new JLabel ("Enter the final modifier  below.  (-99 to 99)");
                    modifierLabel.setForeground(darkGold);
                    modifierLabel.setHorizontalAlignment(modifierLabel.CENTER);

        JTextField  inputModifier           = new JTextField("2");
                    inputModifier.setBackground(darkCoal);
                    inputModifier.setForeground(darkGold);
                    inputModifier.setHorizontalAlignment(inputModifier.CENTER);

        JButton     newRollButton           = new JButton("ROLL");
                    newRollButton.setBackground(darkCoal);
                    newRollButton.setForeground(darkGold);
                    newRollButton.addActionListener(this);

        JButton     helpButton              = new JButton("Help/About");
                    helpButton.setBackground(darkCoal);
                    helpButton.setForeground(ltSilver);
                    helpButton.addActionListener(this);

        JButton     exitButton              = new JButton("Exit");
                    exitButton.setBackground(darkCoal);
                    exitButton.setForeground(crimson);
                    exitButton.addActionListener(this);

        //Conversions
                    getSides                = inputSides.getText();
                    getDice                 = inputDice.getText();
                    getModifier             = inputModifier.getText();
                    sidesToRoll             = Integer.parseInt(getSides);
                    diceToRoll              = Integer.parseInt(getDice);
                    modifier                = Integer.parseInt(getModifier);
                    diceLeft                = diceToRoll;
                    //rollResultTotal       = rollResultTotal;

        // Paneling
        rollPanel.setLayout(new GridLayout (3,3));
        rollPanel.setBackground(darkPurple);
        rollPanel.setForeground(darkGold);
        rollPanel.add(sidesLabel);
        rollPanel.add(diceLabel);
        rollPanel.add(modifierLabel);
        rollPanel.add(inputSides);
        rollPanel.add(inputDice);
        rollPanel.add(inputModifier);
        rollPanel.add(newRollButton);
        rollPanel.add(helpButton);
        rollPanel.add(exitButton);
    }

    // Implement ActionListener for multiple JButtons
    public void actionPerformed(ActionEvent e)
    {
        String arg = e.getActionCommand();
        if ("Help/About".equals(arg))
            {
                JOptionPane.showMessageDialog(null,"This application generates random values, based on the parameters input by the user.\nPlease choose number of dice, sides on each die, and a +/- roll modifier.\nIf no roll modifier is needed, enter 0 (numeric zero) in the modifier field.\n(The starting numbers tell the program to roll 3 six-sided dice and add 2 or '3d6+2'.)","Help/About",JOptionPane.INFORMATION_MESSAGE);
            }

        if ("Exit".equals(arg))
            {
                System.exit(0);
            }

        if ("ROLL".equals(arg))

                {
                    try
                    {
                        while (diceLeft>0)
                        {
                            getSides                    = inputSides.getText();
                            sidesToRoll                 = Integer.parseInt(getSides);
                            if(sidesToRoll<1 || sidesToRoll>99)     throw new NumberFormatException();
                            else

                            getDice                     = inputDice.getText();
                            diceToRoll                  = Integer.parseInt(getDice);
                            if(diceToRoll<1 || diceToRoll>99)       throw new NumberFormatException();
                            else

                            getModifier                 = inputModifier.getText();
                            modifier                    = Integer.parseInt(getModifier);
                            if(modifier<-99 || modifier>99)         throw new NumberFormatException();
                            else

                        rollResult                  = roll.nextInt(sidesToRoll)+1;
                        rollResultTotal             = rollResultTotal + rollResult;
                        diceLeft--;
                        }

                    }


                    catch(NumberFormatException ex)
                    {
                        JOptionPane.showMessageDialog(null,"You must enter an integer within the given range of each field.","ROLL",JOptionPane.INFORMATION_MESSAGE);
                        diceLeft = 0;
                    }


                    {   //Display the Roll Formula and Result
                    JOptionPane.showMessageDialog(null,"You entered a roll of " + (diceToRoll) + "d" + (sidesToRoll) + "+(" + (modifier) + ").\nYou rolled " + (rollResultTotal) + "!");
                    }
        ;}
    ;}
}

Answer 1

You initialize this member variable, but you never add this field to the UI:

JTextField inputSides = new JTextField(" ");

Here you read from this text field that still contains the String " ", which is not an integer.

getSides = inputSides.getText();
sidesToRoll = Integer.parseInt(getSides);

When you build your UI in the constructor, you declare another, local variable with the same name, pointing to a new object:

JTextField inputSides = new JTextField("6");

This is the object that appears in the UI. The local variable inputSides hides the member variable of the same name.

---

As an aside, this is not the right way to compare strings:

arg == "ROLL"

This only works because arg is pointing to the same, interned object instance. The correct way to compare these values would be:

"ROLL".equals(arg)

---

EDIT:

The trick you are missing is in thinking about the objects you are creating and which ones your reference variables are pointing at.

Consider this simplified version of your code:

public class ObjectReferences {
  private final JLabel label = new JLabel("I am FOO"); // label 1

  public ObjectReferences() {
    JLabel label = new JLabel("I am BAR"); // label 2

    JButton button = new JButton("Click me");
    button.addActionListener(new ActionListener() {
      @Override public void actionPerformed(ActionEvent e) {
        onclick();
      }
    });

    // will display "I am BAR"
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(600, 400);
    frame.setLayout(new FlowLayout());
    frame.add(label); // label 2
    frame.add(button);
    frame.setVisible(true);
  }

  public void onclick() {
    // will display "I am FOO"
    JOptionPane.showMessageDialog(null, label.getText()); // label 1
  }

  public static void main(String[] args) {
    new ObjectReferences();
  }
}

Two label objects are created, but only one is added to the frame. label 1 is referenced by the member variable and this is the one visible to the onclick() method. Within the constructor, label 2 is referenced by a local variable called label that hides the member variable called label.

Your intent is to write something like this instead:

public class ObjectReferences {
  private final JLabel label = new JLabel("I am FOO");

  public ObjectReferences() {
    JButton button = new JButton("Click me");
    button.addActionListener(new ActionListener() {
      @Override public void actionPerformed(ActionEvent e) {
        onclick();
      }
    });

    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(600, 400);
    frame.setLayout(new FlowLayout());
    frame.add(label);
    frame.add(button);
    frame.setVisible(true);
  }

  public void onclick() {
    JOptionPane.showMessageDialog(null, label.getText());
  }

  public static void main(String[] args) {
    new ObjectReferences();
  }
}