Java Dice Roller with GUI

Question

Three days ago I wrote about a Java Dice Roller I wrote. I've now added a GUI to that program. Here it is:

DiceRollerGUI.java:

package com.egroegnosbig.dicerollergui;

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

public class DiceRollerGUI {
    static JFrame frameOne = new JFrame("Dice Roller");
    public static void main(String[] args) {
        frameOne.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        DiceGUI GUI = new DiceGUI();
        frameOne.add(GUI);

        Button b = new Button("Roll");
        b.addActionListener(new ButtonAction());
        frameOne.add(b);
        frameOne.setLayout(new GridLayout(1, 2));
        frameOne.setSize(400, 250);
        frameOne.setResizable(false);
        frameOne.setVisible(true);
    }
}

class ButtonAction implements ActionListener {
    @Override
    public void actionPerformed(ActionEvent e) {
        DiceRollerGUI.frameOne.setVisible(false);
        JFrame frameTwo = new JFrame("Dice Roller");
        frameTwo.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frameTwo.setSize(400, 250);
        frameTwo.setResizable(false);
        ResultGUI resultGUI = new ResultGUI();
        frameTwo.add(resultGUI);
        frameTwo.setVisible(true);
    }
}

DiceGUI.java:

package com.egroegnosbig.dicerollergui;

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

public class DiceGUI extends JPanel {
    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        this.setBackground(Color.WHITE);

        g.drawString("Dice Roller", 70, 20);
    }
}

ResultGUI.java:

package com.egroegnosbig.dicerollergui;

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

public class ResultGUI extends JPanel {
    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        this.setBackground(Color.WHITE);

        Dice dice = new Dice(6);
        int resultInt = dice.roll();
        StringBuilder sb = new StringBuilder();
        sb.append("");
        sb.append(resultInt);
        String result = sb.toString();
        g.drawString("The dice rolled a", 150, 125);
        g.drawString(result, 243, 125);
    }
}

Dice.java:

package com.egroegnosbig.dicerollergui;

import java.util.Random;

public class Dice {
    private final Random rand;
    private final int faces;

    public Dice(int faces) {
        this.rand = new Random();
        this.faces = faces;
    }

    public int roll() {
        return rand.nextInt(faces) + 1;
    }
}

Working on better class names...

Answer 1

• Rather than swapping out the entire JFrame for another on the button click, you should simply be updating the contents. This is all very overwrought. I think all you really need is a panel with a button and a label. Click the button, and display the results in the label.
• Related to the above, rather than overriding paint, you should be using a layout and adding subcomponents.

To get you started:

public class DicePanel extends JPanel {
  private final Dice dice;

  private JButton rollButton;
  private JLabel displayLabel;

  public DicePanel(Dice dice) {
    this.dice = dice;

    rollButton = new JButton("Roll");
    displayLabel = new JLabel();

    rollButton.addActionListener(e ->
      displayLabel.setText("You rolled a: " + dice.roll())
    );
    // or if you're not using Java 8, you can do the more verbose thing.

    // not specifying a layout defaults to a flow layout.  Set a layout via:
    // setLayout(new BorderLayout()); // or whatever
    add(rollButton);
    add(displayLabel);
  }
}

Your program should just create a Dice, create a DicePanel with that, and stick it in a JFrame and show it. Then play around with layouts to get something you like.