Modifying a JTextField after reading String from another JTextField

Question

Having some problems updating a JTextField in a different class after reading a String from another JTextField. Here's the method in question:

public JTextField buyVowel(playerPlate player)
{
    String get = input.getText();
    String[] vowels = new String[]{"a","e","i","o","u"};
    for(int i =0; i<vowels.length; i++)
    {
        if(get.equals(vowels[i]))
        {
            player.pMoney =- 250;
            player.playerMoney.setText("$"+player.pMoney);

        }
    }
    return player.playerMoney;
}

playerPlate is a separate class.

I'm using this method to determine what player the program should be modifying:

public playerPlate getCurrentPlayer()
{
    if(currentPlayer == 1)
    {
        return player1;
    }
    else if(currentPlayer == 2)
    {
        return player2;
    }
    else
    {
        return player3;
    }
}

player(s) 1, 2, and 3 are instances of playerPlate.

I want it to be modifying instance variables in this class:

package wheelOfFortune;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class playerPlate extends JPanel
                            implements ActionListener
{
public String pName;
public int pMoney = 500;
public int currentPlayer;
public JTextField playerMoney;

public playerPlate(String player, Color color, int currentPlayer)
{
    setBorder(BorderFactory.createLineBorder(Color.BLACK,2));
    setBackground(color);
    pName = player;
    JTextField playerNames = new JTextField(pName);
    playerNames.setBorder(BorderFactory.createLineBorder(Color.BLACK,2));
    playerNames.setEditable(false);
    playerNames.setFont(new Font("Impact", Font.PLAIN, 24));
    playerNames.setHorizontalAlignment(JTextField.CENTER);
    playerNames.setBackground(Color.WHITE);

    JTextField playerMoney = new JTextField("$"+pMoney);
    playerMoney.setBorder(BorderFactory.createLineBorder(Color.BLACK,2));
    playerMoney.setEditable(false);
    playerMoney.setFont(new Font("Impact", Font.BOLD, 32));
    playerMoney.setHorizontalAlignment(JTextField.CENTER);
    playerMoney.setBackground(Color.WHITE);

    Box b1 = Box.createVerticalBox();
    b1.add(playerNames);
    b1.add(Box.createVerticalStrut(5));
    Box b2 = Box.createHorizontalBox();
    b2.add(Box.createHorizontalStrut(60));
    Box b3 = Box.createVerticalBox();
    b3.add(playerMoney);
    b3.add(Box.createVerticalStrut(8));
    b2.add(b3);
    b1.add(b2);
    b1.add(Box.createVerticalStrut(5));
    add(b1);    
}
public void actionPerformed(ActionEvent e) 
{

}
}

Here is the actionPerformed method within the main class:

public void actionPerformed(ActionEvent e) 
{
    JButton b = (JButton)e.getSource();
    if(b==spin)
    {
        spinWheel(wheelStuff);
        repaint();
    }
    if(b==next)
    {
        updatePlayer();
        repaint();
    }
    if(b==reset)
    {
        letterBoard.reset();
        updateCat();
        repaint();
    }
    if(b==buyVowel)
    {
        buyVowel(getCurrentPlayer());
        repaint();
    }
}

The gist of what I want to happen, is when the user types a vowel into JTextField input, and clicks JButton buyVowel it subtracts $250 from their total money (pMoney). And displays the change on the GUI. After tinkering with this for a couple hours, I honestly have no idea why this isn't working. I keep receiving nullPointerExceptions when trying to use it. Thanks for your help.

Note: everything except for class playerPlate is in the same class. playerPlate is in a separate class.

Answer 1

You're shadowing the variable playerMoney in the constructor of playerPlate. The method buyVowel relies on playerPlate being instantiated when invoking setText, otherwise a NullPointerException will be thrown. Replace

JTextField playerMoney = new JTextField("$"+pMoney);

with

playerMoney = new JTextField("$"+pMoney);

Aside: Java naming conventions indicate that class names start with uppcase letters so use class names such as PlayerPlate.