Develop Reference

My content pane show only white even if it has components on it

I'm doing this as a challenge for myself. My problem is that when I click on the button, the content pane appears plain even if the JPanel has components in it.
I've tried adding the components on the frame but I get an error: >Cannot read field "parent" because "comp" is null.
I've tried other layout on JFrame and JPanel and still it didn't show.
Here's the full code:
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;
public class test implements ActionListener{
public static void main(String [] args) {
new test();
}
static JPanel mainPanel, cubePanel;
static JFrame frame;
static Container container = new Container();
static JLabel calculatorFor;
static JButton sphereButton, rightCylinderButton, rightConeButton, rectangularPrismButton, triangularPrismButton,
cubeButton, squarePyramidButton, rectangularPyramidButton, ellipsoidButton, tetrahedronButton ,backToPreviousFrameButton;
static Font font = new Font(null, Font.PLAIN, 30);
static JLabel enterValueForEdge;
static JTextField edgeTextField;
static JTextArea surfaceAreaTextArea, surfaceAreaFormulaTextArea, surfaceAreaSolutionTextArea;
static JButton calculateButton;
static double edge;
static DecimalFormat surfaceAreaDecimal;
public test(){
frame = new JFrame("Calculating for Surface Area");
calculatorFor = new JLabel("Calculator for the Surface Area of:");
calculatorFor.setSize(600, 40);
calculatorFor.setLocation(100, 50);
calculatorFor.setFont(font);
calculatorFor.setFocusable(false);
sphereButton = new JButton("Sphere ");
sphereButton.setSize(400, 40);
sphereButton.setLocation(100, 100);
sphereButton.setFont(font);
sphereButton.addActionListener(this);
sphereButton.setFocusable(false);
rightCylinderButton = new JButton("Right Cylinder");
rightCylinderButton.setSize(400, 40);
rightCylinderButton.setLocation(100, 150);
rightCylinderButton.setFont(font);
rightCylinderButton.addActionListener(this);
rightCylinderButton.setFocusable(false);
rightConeButton = new JButton("Right Cone");
rightConeButton.setSize(400, 40);
rightConeButton.setLocation(100, 200);
rightConeButton.setFont(font);
rightConeButton.addActionListener(this);
rightConeButton.setFocusable(false);
rectangularPrismButton = new JButton("Rectangular Prism");
rectangularPrismButton.setSize(400, 40);
rectangularPrismButton.setLocation(100, 250);
rectangularPrismButton.setFont(font);
rectangularPrismButton.addActionListener(this);
rectangularPrismButton.setFocusable(false);
triangularPrismButton = new JButton("Triangular Prism");
triangularPrismButton.setSize(400, 40);
triangularPrismButton.setLocation(100, 300);
triangularPrismButton.setFont(font);
triangularPrismButton.addActionListener(this);
triangularPrismButton.setFocusable(false);
cubeButton = new JButton("Cube");
cubeButton.setSize(400, 40);
cubeButton.setLocation(100, 350);
cubeButton.setFont(font);
cubeButton.addActionListener(this);
cubeButton.setFocusable(false);
squarePyramidButton = new JButton("Square Pyramid");
squarePyramidButton.setSize(400, 40);
squarePyramidButton.setLocation(100, 400);
squarePyramidButton.setFont(font);
squarePyramidButton.addActionListener(this);
squarePyramidButton.setFocusable(false);
rectangularPyramidButton = new JButton("Rectangular Pyramid");
rectangularPyramidButton.setSize(400, 40);
rectangularPyramidButton.setLocation(100, 450);
rectangularPyramidButton.setFont(font);
rectangularPyramidButton.addActionListener(this);
rectangularPyramidButton.setFocusable(false);
ellipsoidButton = new JButton("Ellipsoid");
ellipsoidButton.setSize(400, 40);
ellipsoidButton.setLocation(100, 500);
ellipsoidButton.setFont(font);
ellipsoidButton.addActionListener(this);
ellipsoidButton.setFocusable(false);
tetrahedronButton = new JButton("Tetrahedron");
tetrahedronButton.setSize(400, 40);
tetrahedronButton.setLocation(100, 550);
tetrahedronButton.setFont(font);
tetrahedronButton.addActionListener(this);
tetrahedronButton.setFocusable(false);
backToPreviousFrameButton = new JButton("Back");
backToPreviousFrameButton.setSize(100, 40);
backToPreviousFrameButton.setLocation(900, 600);
backToPreviousFrameButton.setFont(font);
backToPreviousFrameButton.addActionListener(this);
backToPreviousFrameButton.setFocusable(false);
mainPanel = new JPanel();
mainPanel.setBounds(0, 0, 1080, 720);
mainPanel.setLayout(null);
mainPanel.setBackground(Color.decode("#FAF7FC"));
mainPanel.add(calculatorFor);
mainPanel.add(sphereButton);
mainPanel.add(rightCylinderButton);
mainPanel.add(rightConeButton);
mainPanel.add(rectangularPrismButton);
mainPanel.add(triangularPrismButton);
mainPanel.add(cubeButton);
mainPanel.add(squarePyramidButton);
mainPanel.add(rectangularPyramidButton);
mainPanel.add(ellipsoidButton);
mainPanel.add(tetrahedronButton);
mainPanel.add(backToPreviousFrameButton);
frame.getContentPane().add(mainPanel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setBackground(Color.decode("#FAF7FC"));
frame.setLayout(new BorderLayout());
frame.setSize(1080,720);
frame.setResizable(false);
frame.setVisible(true);
frame.setLocationRelativeTo(null);
}
public void cubePanel(){
enterValueForEdge = new JLabel("Enter Edge:");
enterValueForEdge.setSize(200, 40);
enterValueForEdge.setLocation(100, 50);
enterValueForEdge.setFont(font);
enterValueForEdge.setFocusable(false);
edgeTextField = new JTextField();
edgeTextField.setSize(400, 40);
edgeTextField.setLocation(300, 50);
edgeTextField.setFont(font);
calculateButton = new JButton("Calculate");
calculateButton.setSize(200, 40);
calculateButton.setLocation(100, 100);
calculateButton.setFont(font);
calculateButton.addActionListener(this);
calculateButton.setFocusable(false);
surfaceAreaFormulaTextArea = new JTextArea("SA = 6a²");
surfaceAreaFormulaTextArea.setSize(400, 40);
surfaceAreaFormulaTextArea.setLocation(100, 150);
surfaceAreaFormulaTextArea.setFont(font);
surfaceAreaFormulaTextArea.setEditable(false);
surfaceAreaTextArea = new JTextArea("SA: ");
surfaceAreaTextArea.setSize(500, 40);
surfaceAreaTextArea.setLocation(100, 200);
surfaceAreaTextArea.setFont(font);
surfaceAreaTextArea.setEditable(false);
surfaceAreaSolutionTextArea = new JTextArea();
surfaceAreaSolutionTextArea.setSize(900, 80);
surfaceAreaSolutionTextArea.setLocation(100, 250);
surfaceAreaSolutionTextArea.setFont(font);
surfaceAreaSolutionTextArea.setEditable(false);
surfaceAreaSolutionTextArea.setLineWrap(true);
backToPreviousFrameButton = new JButton("Back");
backToPreviousFrameButton.setSize(100, 40);
backToPreviousFrameButton.setLocation(900, 600);
backToPreviousFrameButton.setFont(font);
backToPreviousFrameButton.addActionListener(this);
backToPreviousFrameButton.setFocusable(false);
cubePanel = new JPanel();
cubePanel.setBounds(0, 0, 1080, 720);
cubePanel.setLayout(null);
cubePanel.setBackground(Color.decode("#FAF7FC"));
container = new Container();
cubePanel.add(enterValueForEdge);
cubePanel.add(edgeTextField);
cubePanel.add(calculateButton);
cubePanel.add(surfaceAreaFormulaTextArea);
cubePanel.add(surfaceAreaTextArea);
cubePanel.add(surfaceAreaSolutionTextArea);
cubePanel.add(backToPreviousFrameButton);
container.add(cubePanel);
container.setLayout(null);
container.setBackground(Color.decode("#FAF7FH"));
}
#Override
public void actionPerformed(ActionEvent e) {
if(e.getSource() == sphereButton){
new sphereFrame();
frame.dispose();
}
if(e.getSource() == rightCylinderButton){
new rightCylinderFrame();
frame.dispose();
}
if(e.getSource() == rightConeButton){
new rightConeFrame();
frame.dispose();
}
if(e.getSource() == rectangularPrismButton){
new rectangularPrismFrame();
frame.dispose();
}
if(e.getSource() == triangularPrismButton){
new triangularPrismFrame();
frame.dispose();
}
if(e.getSource() == cubeButton){
frame.getContentPane().removeAll();
frame.add(cubePanel);
frame.repaint();
frame.revalidate();
System.out.println("Remove");
frame.getContentPane().add(container);
}
}

Oracle has a helpful tutorial, Creating a GUI With Swing. Skip the Learning Swing with the NetBeans IDE section. Pay particular attention to the Laying Out Components Within a Container section.
Here's the GUI I created.
Press the "Cube" button to bring up the page for the cube calculation.
All Swing applications must start with a call to the SwingUtilities invokeLater method. This method ensures that the Swing components are created and executed on the Event Dispatch Thread.
The JFrame has a default BorderLayout and holds the main JPanel. The main JPanel uses a CardLayout to display the various calculation JPanels. Using a CardLayout is much easier than managing multiple JFrames and provides a nicer user experience.
I used Swing layout managers to position the Swing components on the various JPanels.
The start JPanel consists of two subordinate JPanels. The title JPanel uses a FlowLayout to display the title. The button JPanel uses a GridLayout to display the various calculation JButtons. You can create complex JPanels by nesting multiple simple JPanels.
The cube calculation JPanel was the only one you had in your code, so it was the only one I created. I made it a method, but you can create a separate class for each of the calculations. The cube calculation JPanel uses a GridBagLayout to create a form-like JPanel. I used lambda expressions to create the ActionListener for each of the JButtons, since they were so simple.
I made the start JPanel button ActionListener a separate class just to get the code away from the for loop that creates the JButtons.
Here's the complete runnable code.
import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class CardLayoutGUI implements Runnable {
public static void main(String[] args) {
SwingUtilities.invokeLater(new CardLayoutGUI());
}
private CardLayout cardLayout;
private JTextField edgeTextField, surfaceAreaSolutionTextField;
private JPanel mainPanel;
#Override
public void run() {
JFrame frame = new JFrame("Calculating for Surface Area");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.mainPanel = createMainPanel();
frame.add(mainPanel, BorderLayout.CENTER);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel createMainPanel() {
cardLayout = new CardLayout();
JPanel panel = new JPanel(cardLayout);
panel.setBorder(BorderFactory.createEmptyBorder(0, 5, 5, 5));
panel.add(createStartPanel(), "Start");
panel.add(createCubeCalculationPanel(), "Cube");
return panel;
}
private JPanel createStartPanel() {
JPanel panel = new JPanel(new BorderLayout());
panel.setBorder(BorderFactory.createEmptyBorder(0, 5, 5, 5));
panel.add(createTitlePanel(), BorderLayout.NORTH);
panel.add(createButtonPanel(), BorderLayout.CENTER);
return panel;
}
private JPanel createTitlePanel() {
JPanel panel = new JPanel(new FlowLayout());
panel.setBorder(BorderFactory.createEmptyBorder(0, 5, 5, 5));
Font font = new Font(Font.DIALOG, Font.PLAIN, 36);
JLabel label = new JLabel("Calculator for the Surface Area of:");
label.setFont(font);
panel.add(label);
return panel;
}
private JPanel createButtonPanel() {
String[] text = { "Sphere", "Right Cylinder", "Right Cone",
"Rectangular Prism", "Triangular Prism", "Cube",
"Square Pyramid", "Rectangular Pyramid", "Ellipsoid",
"Tetrahedron" };
JPanel panel = new JPanel(new GridLayout(0, 3, 5, 5));
panel.setBorder(BorderFactory.createEmptyBorder(0, 5, 5, 5));
Font font = new Font(null, Font.PLAIN, 24);
ButtonListener listener = new ButtonListener();
for (String s : text) {
JButton button = new JButton(s);
button.addActionListener(listener);
button.setFont(font);
panel.add(button);
}
return panel;
}
private JPanel createCubeCalculationPanel() {
JPanel panel = new JPanel(new GridBagLayout());
panel.setBorder(BorderFactory.createEmptyBorder(0, 5, 5, 5));
Font titleFont = new Font(null, Font.PLAIN, 32);
Font font = new Font(null, Font.PLAIN, 16);
GridBagConstraints gbc = new GridBagConstraints();
gbc.anchor = GridBagConstraints.LINE_START;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.insets = new Insets(0, 5, 5, 5);
gbc.weighty = 1.0;
gbc.gridwidth = 2;
gbc.gridx = 0;
gbc.gridy = 0;
JLabel label = new JLabel("SA = 6a²");
label.setFont(titleFont);
panel.add(label, gbc);
gbc.gridwidth = 1;
gbc.gridy++;
label = new JLabel("Edge:");
label.setFont(font);
panel.add(label, gbc);
gbc.gridx++;
edgeTextField = new JTextField(10);
edgeTextField.setFont(font);
panel.add(edgeTextField, gbc);
gbc.gridx = 0;
gbc.gridy++;
label = new JLabel("SA:");
label.setFont(font);
panel.add(label, gbc);
gbc.gridx++;
surfaceAreaSolutionTextField = new JTextField(10);
surfaceAreaSolutionTextField.setFont(font);
surfaceAreaSolutionTextField.setEditable(false);
panel.add(surfaceAreaSolutionTextField, gbc);
gbc.gridwidth = 2;
gbc.gridx = 0;
gbc.gridy++;
JButton calculateButton = new JButton("Calculate");
calculateButton.addActionListener(event -> {
double edge = Double.valueOf(edgeTextField.getText());
double sa = 6.0 * edge * edge;
surfaceAreaSolutionTextField.setText(Double.toString(sa));
});
calculateButton.setFont(font);
panel.add(calculateButton, gbc);
gbc.gridy++;
JButton backButton = new JButton("Back");
backButton.addActionListener(event -> {
cardLayout.show(mainPanel, "Start");
});
backButton.setFont(font);
panel.add(backButton, gbc);
return panel;
}
public class ButtonListener implements ActionListener {
#Override
public void actionPerformed(ActionEvent event) {
JButton button = (JButton) event.getSource();
String text = button.getText();
cardLayout.show(mainPanel, text);
}
}
}

Try this :
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;
public class Test2 implements ActionListener {
public static void main(String[] args) {
new Test2();
}
static JPanel mainPanel, cubePanel;
static JFrame frame;
static Container container = new Container();
static JLabel calculatorFor;
static JButton sphereButton, rightCylinderButton, rightConeButton, rectangularPrismButton, triangularPrismButton,
cubeButton, squarePyramidButton, rectangularPyramidButton, ellipsoidButton, tetrahedronButton, backToPreviousFrameButton;
static Font font = new Font(null, Font.PLAIN, 30);
static JLabel enterValueForEdge;
static JTextField edgeTextField;
static JTextArea surfaceAreaTextArea, surfaceAreaFormulaTextArea, surfaceAreaSolutionTextArea;
static JButton calculateButton;
static double edge;
static DecimalFormat surfaceAreaDecimal;
public Test2() {
frame = new JFrame("Calculating for Surface Area");
calculatorFor = new JLabel("Calculator for the Surface Area of:");
calculatorFor.setSize(600, 40);
calculatorFor.setLocation(100, 50);
calculatorFor.setFont(font);
calculatorFor.setFocusable(false);
sphereButton = new JButton("Sphere ");
sphereButton.setSize(400, 40);
sphereButton.setLocation(100, 100);
sphereButton.setFont(font);
sphereButton.addActionListener(this);
sphereButton.setFocusable(false);
rightCylinderButton = new JButton("Right Cylinder");
rightCylinderButton.setSize(400, 40);
rightCylinderButton.setLocation(100, 150);
rightCylinderButton.setFont(font);
rightCylinderButton.addActionListener(this);
rightCylinderButton.setFocusable(false);
rightConeButton = new JButton("Right Cone");
rightConeButton.setSize(400, 40);
rightConeButton.setLocation(100, 200);
rightConeButton.setFont(font);
rightConeButton.addActionListener(this);
rightConeButton.setFocusable(false);
rectangularPrismButton = new JButton("Rectangular Prism");
rectangularPrismButton.setSize(400, 40);
rectangularPrismButton.setLocation(100, 250);
rectangularPrismButton.setFont(font);
rectangularPrismButton.addActionListener(this);
rectangularPrismButton.setFocusable(false);
triangularPrismButton = new JButton("Triangular Prism");
triangularPrismButton.setSize(400, 40);
triangularPrismButton.setLocation(100, 300);
triangularPrismButton.setFont(font);
triangularPrismButton.addActionListener(this);
triangularPrismButton.setFocusable(false);
cubeButton = new JButton("Cube");
cubeButton.setSize(400, 40);
cubeButton.setLocation(100, 350);
cubeButton.setFont(font);
cubeButton.addActionListener(this);
cubeButton.setFocusable(false);
squarePyramidButton = new JButton("Square Pyramid");
squarePyramidButton.setSize(400, 40);
squarePyramidButton.setLocation(100, 400);
squarePyramidButton.setFont(font);
squarePyramidButton.addActionListener(this);
squarePyramidButton.setFocusable(false);
rectangularPyramidButton = new JButton("Rectangular Pyramid");
rectangularPyramidButton.setSize(400, 40);
rectangularPyramidButton.setLocation(100, 450);
rectangularPyramidButton.setFont(font);
rectangularPyramidButton.addActionListener(this);
rectangularPyramidButton.setFocusable(false);
ellipsoidButton = new JButton("Ellipsoid");
ellipsoidButton.setSize(400, 40);
ellipsoidButton.setLocation(100, 500);
ellipsoidButton.setFont(font);
ellipsoidButton.addActionListener(this);
ellipsoidButton.setFocusable(false);
tetrahedronButton = new JButton("Tetrahedron");
tetrahedronButton.setSize(400, 40);
tetrahedronButton.setLocation(100, 550);
tetrahedronButton.setFont(font);
tetrahedronButton.addActionListener(this);
tetrahedronButton.setFocusable(false);
backToPreviousFrameButton = new JButton("Back");
backToPreviousFrameButton.setSize(100, 40);
backToPreviousFrameButton.setLocation(900, 600);
backToPreviousFrameButton.setFont(font);
backToPreviousFrameButton.addActionListener(this);
backToPreviousFrameButton.setFocusable(false);
mainPanel = new JPanel();
mainPanel.setBounds(0, 0, 1080, 720);
mainPanel.setLayout(null);
mainPanel.setBackground(Color.decode("#FAF7FC"));
mainPanel.add(calculatorFor);
mainPanel.add(sphereButton);
mainPanel.add(rightCylinderButton);
mainPanel.add(rightConeButton);
mainPanel.add(rectangularPrismButton);
mainPanel.add(triangularPrismButton);
mainPanel.add(cubeButton);
mainPanel.add(squarePyramidButton);
mainPanel.add(rectangularPyramidButton);
mainPanel.add(ellipsoidButton);
mainPanel.add(tetrahedronButton);
mainPanel.add(backToPreviousFrameButton);
frame.getContentPane().add(mainPanel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setBackground(Color.decode("#FAF7FC"));
frame.setLayout(new BorderLayout());
frame.setSize(1080, 720);
frame.setResizable(false);
frame.setVisible(true);
frame.setLocationRelativeTo(null);
}
public Container cubePanel() {
enterValueForEdge = new JLabel("Enter Edge:");
enterValueForEdge.setSize(200, 40);
enterValueForEdge.setLocation(100, 50);
enterValueForEdge.setFont(font);
enterValueForEdge.setFocusable(false);
edgeTextField = new JTextField();
edgeTextField.setSize(400, 40);
edgeTextField.setLocation(300, 50);
edgeTextField.setFont(font);
calculateButton = new JButton("Calculate");
calculateButton.setSize(200, 40);
calculateButton.setLocation(100, 100);
calculateButton.setFont(font);
calculateButton.addActionListener(this);
calculateButton.setFocusable(false);
surfaceAreaFormulaTextArea = new JTextArea("SA = 6a²");
surfaceAreaFormulaTextArea.setSize(400, 40);
surfaceAreaFormulaTextArea.setLocation(100, 150);
surfaceAreaFormulaTextArea.setFont(font);
surfaceAreaFormulaTextArea.setEditable(false);
surfaceAreaTextArea = new JTextArea("SA: ");
surfaceAreaTextArea.setSize(500, 40);
surfaceAreaTextArea.setLocation(100, 200);
surfaceAreaTextArea.setFont(font);
surfaceAreaTextArea.setEditable(false);
surfaceAreaSolutionTextArea = new JTextArea();
surfaceAreaSolutionTextArea.setSize(900, 80);
surfaceAreaSolutionTextArea.setLocation(100, 250);
surfaceAreaSolutionTextArea.setFont(font);
surfaceAreaSolutionTextArea.setEditable(false);
surfaceAreaSolutionTextArea.setLineWrap(true);
backToPreviousFrameButton = new JButton("Back");
backToPreviousFrameButton.setSize(100, 40);
backToPreviousFrameButton.setLocation(900, 600);
backToPreviousFrameButton.setFont(font);
backToPreviousFrameButton.addActionListener(this);
backToPreviousFrameButton.setFocusable(false);
cubePanel = new JPanel();
cubePanel.setBounds(0, 0, 1080, 720);
cubePanel.setLayout(null);
cubePanel.setBackground(Color.decode("#FAF7FC"));
container = new Container();
cubePanel.add(enterValueForEdge);
cubePanel.add(edgeTextField);
cubePanel.add(calculateButton);
cubePanel.add(surfaceAreaFormulaTextArea);
cubePanel.add(surfaceAreaTextArea);
cubePanel.add(surfaceAreaSolutionTextArea);
cubePanel.add(backToPreviousFrameButton);
container.add(cubePanel);
container.setLayout(null);
container.setBackground(Color.getColor("#FAF7FH"));
return container;
}
#Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == sphereButton) {
new sphereFrame();
frame.dispose();
}
if (e.getSource() == rightCylinderButton) {
new rightCylinderFrame();
frame.dispose();
}
if (e.getSource() == rightConeButton) {
new rightConeFrame();
frame.dispose();
}
if (e.getSource() == rectangularPrismButton) {
new rectangularPrismFrame();
frame.dispose();
}
if (e.getSource() == triangularPrismButton) {
//new triangularPrismFrame();
frame.dispose();
}
if (e.getSource() == cubeButton) {
frame.getContentPane().removeAll();
frame.add(cubePanel());
frame.repaint();
frame.revalidate();
System.out.println("Remove");
frame.getContentPane().add(container);
}
}
}

Why does this only work on designed comboBox and not on hardcoded swing?

Newbie question:
So this code here
public void comboItemItemStateChanged(java.awt.event.ItemEvent evt) {
ArrayList<String> arrayItem = new ArrayList<>();
Iterator<String> iter;
if(comboGroup.getSelectedItem().equals("Betta Fish")){
comboItem.removeAllItems();
arrayItem.add("Plakat");
arrayItem.add("Halfmoon");
arrayItem.add("Crown Tail");
arrayItem.add("Double Tail");
iter = arrayItem.iterator();
while(iter.hasNext()){
comboItem.addItem(iter.next());
}
}
else if(comboGroup.getSelectedItem().equals("Snails")){
comboItem.removeAllItems();
arrayItem.add("Apple Horn");
arrayItem.add("RamsHorn");
arrayItem.add("Pond Snail");
arrayItem.add("Assassin Snail");
iter = arrayItem.iterator();
while(iter.hasNext()){
comboItem.addItem(iter.next());
}
works when I try it on comboBoxes from Design tab in NetBeans. But when I try to apply it to my coded ComboBox, I get a message from evt saying Unused method parameters should be removed. Can I get an explanation why and what is the alternative for hardcoded comboBox?
Purpose of code: a dynamic comboBox so whatever I pick from comboBox1 will have each own set of lists for comboBox2
NOTE: I also tried to change comboItemItemStateChanged to just itemStatChanged.
Source code of my project: https://github.com/kontext66/GuwiPos/blob/main/GuwiPos
Sorry for the confusion everyone, I do have a main class.
public class Main{
public static void main(String[] args){
new GuwiPos();
new HelpWin();
}
}
Main.java, GuwiPos.java

It's quite simple, really.
The message is just NetBeans informing you that the code of method comboItemItemStateChanged does not reference the method parameter evt. It is not an error nor even a warning. You can ignore it. NetBeans displays these "hints" in its editor when you write code whereas NetBeans GUI builder generates code.
Note that method comboItemItemStateChanged will be called each time an item in the JComboBox is selected and also each time an item is de-selected. I'm guessing that you only want the code to run when an item is selected, hence the first line of method comboItemItemStateChanged should be
if (evt.getStateChange() == ItemEvent.SELECTED) {
and then you are referencing the method parameter and the "hint" will go away.
Refer to How to Write an Item Listener
Edit
I think maybe you would benefit from learning about GUI design. I have never seen one like yours. I would like to know how you arrived at that design. In any case, the below code addresses only the functionality whereby the list in comboItem adjusts depending on the selected item in comboGroup.
In my experience, removing and adding items to the JComboBox via methods removeAllItems and addItem, is very slow. It is much more efficient to simply replace the JComboBox model which is what I have done in the below code. For small lists such as yours, the difference will not be noticed but it increases as the lists get larger.
Also, the [JComboBox] selected item is in the evt parameter to method comboItemItemStateChanged.
Your original code did not add an item listener to comboGroup nor did it have a main method. I have added these in the below code. Note that the item listener is added via a method reference.
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.BorderFactory;
import javax.swing.ComboBoxModel;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.JComboBox;
import java.awt.Color;
import java.awt.EventQueue;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Vector;
import java.awt.event.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
/**
*
* #author kahbg
*/
public class GuwiPos extends JFrame implements ActionListener {
public static final Map<String, ComboBoxModel<String>> LISTS;
JButton buttonBasket;
JButton buttonHelp;
JTextField txtGroup;
JTextField txtItem;
JTextField txtQty;
JTextField txtTotal;
JTextField txtPrice;
JComboBox<String> comboGroup;
JComboBox<String> comboItem;
static {
LISTS = new HashMap<>();
Vector<String> v = new Vector<>();
v.add("Plakat");
v.add("Halfmoon");
v.add("Crown Tail");
v.add("Double Tail");
ComboBoxModel<String> model = new DefaultComboBoxModel<>(v);
LISTS.put("Betta Fish", model);
v = new Vector<>();
v.add("Apple Horn");
v.add("RamsHorn");
v.add("Pond Snail");
v.add("Assassin Snail");
model = new DefaultComboBoxModel<>(v);
LISTS.put("Snails", model);
v = new Vector<>();
v.add("Small Fine Net");
v.add("Large Fine Net");
v.add("Flaring Mirror");
v.add("Aquarium Hose");
model = new DefaultComboBoxModel<>(v);
LISTS.put("Supplies", model);
v = new Vector<>();
v.add("Tubifex");
v.add("Daphnia");
v.add("Optimum Pellets");
model = new DefaultComboBoxModel<>(v);
LISTS.put("Food", model);
}
GuwiPos() {
// ComboBox
String[] products = {"Select Item...", "Betta Fish", "Snails", "Supplies", "Food"};
comboGroup = new JComboBox<String>(products);
comboGroup.addItemListener(this::comboItemItemStateChanged);
comboGroup.setBounds(130, 35, 150, 40);
comboItem = new JComboBox<String>();
comboItem.setBounds(130, 85, 150, 40);
// TextFields
txtPrice = new JTextField();
txtPrice.setBounds(130, 135, 150, 40);
txtQty = new JTextField();
txtQty.setBounds(130, 185, 150, 40);
txtTotal = new JTextField();
txtTotal.setBounds(130, 235, 150, 40);
// txtTotalAmt = new JTextField(); to code later on
// txtPaid = new JTextField(); to code later on
// txtChange = new JTextField(); to code later on
// Labels
// Product
JLabel labelProduct = new JLabel();
labelProduct.setText("Item Group");
labelProduct.setBounds(10, 5, 100, 100);
// Item
JLabel labelItem = new JLabel();
labelItem.setText("Item");
labelItem.setBounds(10, 55, 100, 100);
// Price
JLabel labelPrice = new JLabel();
labelPrice.setText("Price");
labelPrice.setBounds(10, 105, 100, 100);
// Qty
JLabel labelQty = new JLabel();
labelQty.setText("Quantity");
labelQty.setBounds(10, 155, 100, 100);
// Total
JLabel labelTotal = new JLabel();
labelTotal.setText("Total");
labelTotal.setBounds(10, 205, 100, 100);
// Buttons
buttonBasket = new JButton();
buttonBasket.setBounds(0, 0, 300, 50);
buttonBasket.setText("Add to Basket");
buttonBasket.setFocusable(false);
buttonBasket.setBorder(BorderFactory.createEtchedBorder());
buttonBasket.addActionListener(this);
JButton buttonPay = new JButton();
buttonPay.setText("PAY");
buttonPay.setBounds(0, 50, 150, 100);
buttonPay.setFocusable(false);
buttonPay.setBorder(BorderFactory.createEtchedBorder());
buttonPay.addActionListener(e -> System.out.println("Payment Success"));
JButton buttonCancel = new JButton();
buttonCancel.setText("CANCEL");
buttonCancel.setBounds(0, 150, 150, 100);
buttonCancel.setFocusable(false);
buttonCancel.setBorder(BorderFactory.createEtchedBorder());
buttonCancel.addActionListener(e -> System.out.println("Transaction Cancelled"));
JButton buttonDiscount = new JButton();
buttonDiscount.setText("Apply Discount?");
buttonDiscount.setBounds(150, 50, 150, 50);
buttonDiscount.setFocusable(false);
buttonDiscount.setBorder(BorderFactory.createEtchedBorder());
buttonDiscount.addActionListener(e -> System.out.println("20% Discount Applied"));
JButton buttonHelp = new JButton();
buttonHelp.setText("HELP");
buttonHelp.setBounds(150, 100, 150, 100);
buttonHelp.setFocusable(false);
buttonHelp.setBorder(BorderFactory.createEtchedBorder());
JButton buttonDelete = new JButton();
buttonDelete.setText("DELETE");
buttonDelete.setBounds(150, 200, 150, 50);
buttonDelete.setFocusable(false);
buttonDelete.setBorder(BorderFactory.createEtchedBorder());
buttonDelete.addActionListener(e -> System.out.println("Item Deleted"));
// Panels
// Left contains item and price
JPanel bluePanel = new JPanel();
bluePanel.setBackground(Color.blue);
bluePanel.setBounds(0, 0, 300, 300); // x,y,width,height
bluePanel.setLayout(null);
// Right contains product basket
JPanel redPanel = new JPanel();
redPanel.setBackground(Color.red);
redPanel.setBounds(300, 0, 600, 300); // x,y,width,length
redPanel.setLayout(null);
// Bottom Left contains buttons pay,change,discount
JPanel greenPanel = new JPanel();
greenPanel.setBackground(Color.green);
greenPanel.setBounds(0, 300, 300, 450);// x,y,width,length
greenPanel.setLayout(null);
// Bottom Right contains total amount
JPanel yellowPanel = new JPanel();
yellowPanel.setBackground(Color.yellow);
yellowPanel.setBounds(0, 300, 900, 450);// x,y,width,length
yellowPanel.setLayout(null);
this.setTitle("Open Betta POS");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setLayout(null);
this.setSize(900, 590);
this.setResizable(false);
this.setVisible(true);
// ADDED AWT
bluePanel.add(txtQty);
bluePanel.add(txtTotal);
bluePanel.add(txtPrice);
bluePanel.add(comboItem);
bluePanel.add(comboGroup);
bluePanel.add(labelProduct);
bluePanel.add(labelItem);
bluePanel.add(labelPrice);
bluePanel.add(labelQty);
bluePanel.add(labelTotal);
greenPanel.add(buttonBasket);
greenPanel.add(buttonPay);
greenPanel.add(buttonCancel);
greenPanel.add(buttonDiscount);
greenPanel.add(buttonHelp);
greenPanel.add(buttonDelete);
this.add(bluePanel);
this.add(redPanel);
this.add(greenPanel);
this.add(yellowPanel);
}
#Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == buttonBasket) {
System.out.println("Added Item to Basket: " + comboGroup.getSelectedItem() + "\n"
+ comboItem.getSelectedItem());
}
}
// This is not working
public void comboItemItemStateChanged(java.awt.event.ItemEvent evt) {
if (evt.getStateChange() == ItemEvent.SELECTED) {
Object selection = evt.getItem();
ArrayList<String> arrayItem = new ArrayList<>();
Iterator<String> iter;
if (selection.equals("Betta Fish")) {
comboItem.setModel(LISTS.get("Betta Fish"));
}
else if (selection.equals("Snails")) {
comboItem.setModel(LISTS.get("Snails"));
}
else if (selection.equals("Supplies")) {
comboItem.setModel(LISTS.get("Supplies"));
}
else if (selection.equals("Food")) {
comboItem.setModel(LISTS.get("Food"));
}
else if (selection.equals("Select Item...")) {
comboItem.removeAllItems();
arrayItem.add("Select Item...");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
}
}
}
public static void main(String[] args) {
EventQueue.invokeLater(() -> new GuwiPos());
}
}

Your code (improved version - minus one ActionListener)
public class SwingApp {
private static JComboBox<String> comboItem;
private static JComboBox<String> productCombo;
public static void main (String[] args) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run () {
createAndShowGUI();
}
});
}
private static void createAndShowGUI () {
JFrame frame = createMainFrame();
JPanel bluePanel = createBluePanel();
JPanel greenPanel = createGreenPanel();
JPanel redPanel = createRedPanel();
JPanel yellowPanel = createYellowPanel();
frame.add(bluePanel);
frame.add(greenPanel);
frame.add(redPanel);
frame.add(yellowPanel);
frame.setVisible(true);
}
private static JFrame createMainFrame () {
JFrame frame = new JFrame("Open Betta POS");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(null);
frame.setSize(900, 590);
frame.setResizable(false);
return frame;
}
private static JPanel createBluePanel () {
ComboSelectionListener productComboListener = new ComboSelectionListener();
JPanel panel = new JPanel(null); // Sets layout manager to null which is a bad idea!
String[] products =
{"Select Item...", "Betta Fish", "Snails", "Supplies", "Food"};
productCombo = new JComboBox<>(products);
productCombo.setBounds(130, 35, 150, 40);
productCombo.setActionCommand("selectProduct");
productCombo.addActionListener(productComboListener);
comboItem = new JComboBox<>();
comboItem.setBounds(130, 85, 150, 40);
// TextFields
JTextField txtPrice = new JTextField();
txtPrice.setBounds(130, 135, 150, 40);
JTextField txtQty = new JTextField();
txtQty.setBounds(130, 185, 150, 40);
JTextField txtTotal = new JTextField();
txtTotal.setBounds(130, 235, 150, 40);
JLabel labelProduct = new JLabel();
labelProduct.setText("Item Group");
labelProduct.setBounds(10, 5, 100, 100);
// Item
JLabel labelItem = new JLabel();
labelItem.setText("Item");
labelItem.setBounds(10, 55, 100, 100);
// Price
JLabel labelPrice = new JLabel();
labelPrice.setText("Price");
labelPrice.setBounds(10, 105, 100, 100);
// Qty
JLabel labelQty = new JLabel();
labelQty.setText("Quantity");
labelQty.setBounds(10, 155, 100, 100);
// Total
JLabel labelTotal = new JLabel();
labelTotal.setText("Total");
labelTotal.setBounds(10, 205, 100, 100);
panel.setBackground(Color.blue);
panel.setBounds(0, 0, 300, 300); // x,y,width,height
panel.add(txtQty);
panel.add(txtTotal);
panel.add(txtPrice);
panel.add(comboItem);
panel.add(productCombo);
panel.add(labelProduct);
panel.add(labelItem);
panel.add(labelPrice);
panel.add(labelQty);
panel.add(labelTotal);
return panel;
}
private static JPanel createGreenPanel () {
JPanel panel = new JPanel(null);
panel.setBackground(Color.green);
panel.setBounds(0, 300, 300, 450);// x,y,width,length
JButton buttonBasket = new JButton();
buttonBasket.setBounds(0, 0, 300, 50);
buttonBasket.setText("Add to Basket");
buttonBasket.setFocusable(false);
buttonBasket.setBorder(BorderFactory.createEtchedBorder());
buttonBasket
.addActionListener(e -> System.out.println("Added Item to Basket: "
+ productCombo.getSelectedItem() + "\n" + comboItem.getSelectedItem()));
JButton buttonPay = new JButton();
buttonPay.setText("PAY");
buttonPay.setBounds(0, 50, 150, 100);
buttonPay.setFocusable(false);
buttonPay.setBorder(BorderFactory.createEtchedBorder());
buttonPay.addActionListener(e -> System.out.println("Payment Success"));
JButton buttonCancel = new JButton();
buttonCancel.setText("CANCEL");
buttonCancel.setBounds(0, 150, 150, 100);
buttonCancel.setFocusable(false);
buttonCancel.setBorder(BorderFactory.createEtchedBorder());
buttonCancel
.addActionListener(e -> System.out.println("Transaction Cancelled"));
JButton buttonDiscount = new JButton();
buttonDiscount.setText("Apply Discount?");
buttonDiscount.setBounds(150, 50, 150, 50);
buttonDiscount.setFocusable(false);
buttonDiscount.setBorder(BorderFactory.createEtchedBorder());
buttonDiscount
.addActionListener(e -> System.out.println("20% Discount Applied"));
JButton buttonHelp = new JButton();
buttonHelp.setText("HELP");
buttonHelp.setBounds(150, 100, 150, 100);
buttonHelp.setFocusable(false);
buttonHelp.setBorder(BorderFactory.createEtchedBorder());
JButton buttonDelete = new JButton();
buttonDelete.setText("DELETE");
buttonDelete.setBounds(150, 200, 150, 50);
buttonDelete.setFocusable(false);
buttonDelete.setBorder(BorderFactory.createEtchedBorder());
buttonDelete.addActionListener(e -> System.out.println("Item Deleted"));
panel.add(buttonBasket);
panel.add(buttonPay);
panel.add(buttonCancel);
panel.add(buttonDiscount);
panel.add(buttonHelp);
panel.add(buttonDelete);
return panel;
}
private static JPanel createRedPanel () {
JPanel panel = new JPanel(null);
panel.setBackground(Color.red);
panel.setBounds(300, 0, 600, 300); // x,y,width,length
return panel;
}
private static JPanel createYellowPanel () {
JPanel panel = new JPanel();
panel.setBackground(Color.yellow);
panel.setBounds(0, 300, 900, 450); // x,y,width,length
return panel;
}
private static class ComboSelectionListener implements ActionListener {
#Override
public void actionPerformed (ActionEvent e) {
JComboBox<String> comboGroup = (JComboBox<String>) e.getSource();
ArrayList<String> arrayItem = new ArrayList<>();
Iterator<String> iter;
if (comboGroup.getSelectedItem().equals("Betta Fish")) {
comboItem.removeAllItems();
arrayItem.add("Plakat");
arrayItem.add("Halfmoon");
arrayItem.add("Crown Tail");
arrayItem.add("Double Tail");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
} else if (comboGroup.getSelectedItem().equals("Snails")) {
comboItem.removeAllItems();
arrayItem.add("Apple Horn");
arrayItem.add("RamsHorn");
arrayItem.add("Pond Snail");
arrayItem.add("Assassin Snail");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
} else if (comboGroup.getSelectedItem().equals("Supplies")) {
comboItem.removeAllItems();
arrayItem.add("Small Fine Net");
arrayItem.add("Large Fine Net");
arrayItem.add("Flaring Mirror");
arrayItem.add("Aquarium Hose");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
} else if (comboGroup.getSelectedItem().equals("Food")) {
comboItem.removeAllItems();
arrayItem.add("Tubifex");
arrayItem.add("Daphnia");
arrayItem.add("Optimum Pellets");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
} else if (comboGroup.getSelectedItem().equals("Select Item...")) {
comboItem.removeAllItems();
arrayItem.add("Select Item...");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
}
}
}
}
Improvements made (aside from fixing the main issue)
Created a Swing (main) class that is not a Swing component
Main class doesn't implement ActionListener
Used SwingUtilities to launch Swing Application
Created methods to encapsulate the details involving the creation of components
Minimized the scope of variables

I am trying to build a Multiple choice test in java and for some reason my code will only work for two questions and not anymore

This is the code for my quiz.
import java.util.*;
import java.util.List;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Main2 {
public class Questions {
String Question;
String userAns;
String realAns;
}
public static void main(String[] args) {
JFrame frame = new JFrame ("Screen");
frame.setSize(2500, 2500);
frame.setLayout(null);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel();
frame.getContentPane().add(panel);
panel.setSize(2500, 2500);
panel.setLayout(null);
//panel.setBackground(Color.red);
Question[] questions = new Question[2];
System.out.println(questions.length);
Question q1 = new Question();
q1.Question = "1) What is your Name?";
q1.A ="Bob";
q1.B="Billy";
q1.C="Joe";
q1.D="Jill";
questions[0] = q1;
Question q2 = new Question();
q2.Question = "2) What is your Age?";
q2.A ="5";
q2.B="69";
q2.C="21";
q2.D="12";
questions[1] = q2;
/*
Question q3 = new Question();
q3.Question = "3) When Is your Birthday?";
q3.A = "May";
q3.B="Jan";
q3.C="Apr";
q3.D="Aug";
questions[2] = q3;
*/
//When this question is added the code breaks down
JLabel Question = new JLabel(questions[0].Question);
Question.setBounds(50, 0, 1500, 50);
panel.add(Question);
Question.setFont(new Font(Question.getFont().getName(), Font.PLAIN, 25));
Question.setVisible(true);
JLabel incorrectAnswerLabel = new JLabel ("Incorrect Answer! Try Again");
incorrectAnswerLabel.setBounds(300, 0, 1000, 500);
panel.add(incorrectAnswerLabel);
incorrectAnswerLabel.setVisible(false);
incorrectAnswerLabel.setFont(new Font(incorrectAnswerLabel.getFont().getName(), Font.BOLD, 46));
incorrectAnswerLabel.setForeground(Color.RED);
JLabel correctAnswerLabel = new JLabel ("Correct Answer! Good Job");
correctAnswerLabel.setBounds(300, 0, 1000, 500);
panel.add(correctAnswerLabel);
correctAnswerLabel.setVisible(false);
correctAnswerLabel.setFont(new Font(correctAnswerLabel.getFont().getName(), Font.BOLD, 46));
correctAnswerLabel.setForeground(Color.GREEN);
JButton submitButton = new JButton();
submitButton.setBounds(50, 250, 150, 50);
submitButton.setText("Submit");
panel.add(submitButton);
submitButton.setVisible(true);
JRadioButton OptionA = new JRadioButton(questions[0].A);
OptionA.setBounds(50, 50, 100, 50);
panel.add(OptionA);
OptionA.setVisible(true);
JRadioButton OptionB = new JRadioButton(questions[0].B);
OptionB.setBounds(50, 100, 100, 50);
panel.add(OptionB);
OptionB.setVisible(true);
JRadioButton OptionC = new JRadioButton(questions[0].C);
OptionC.setBounds(50, 150, 100, 50);
panel.add(OptionC);
OptionC.setVisible(true);
JRadioButton OptionD = new JRadioButton(questions[0].D);
OptionD.setBounds(50, 200, 100, 50);
panel.add(OptionD);
OptionD.setVisible(true);
ButtonGroup radioGroup = new ButtonGroup();
radioGroup.add(OptionA);
radioGroup.add(OptionB);
radioGroup.add(OptionC);
radioGroup.add(OptionD);
for(int i = 0; i < questions.length-1; i++)
{
final int count = i;
submitButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e)
{
if(submitButton.getText().equals("Submit"))
{
if(OptionA.isSelected()) {
submitButton.setText("Next Question");
correctAnswerLabel.setVisible(true);
}
else
incorrectAnswerLabel.setVisible(true);
}
else {
correctAnswerLabel.setVisible(false);
submitButton.setText("Submit");
Question q = questions[count+1];
Question.setText(q.Question);
setAnswers(q.A, q.B, q.C, q.D, OptionA, OptionB, OptionC, OptionD);
}
}
});
}
}
static void setAnswers(String A, String B,String C,String D, JRadioButton a, JRadioButton b, JRadioButton c, JRadioButton d)
{
List<String> answers = Arrays.asList(A, B,C,D);
Collections.shuffle(answers);
a.setText(answers.get(0));
b.setText(answers.get(1));
c.setText(answers.get(2));
d.setText(answers.get(3));
}
}
My code works fine with only two questions. When I add the third when in it doesn't even show the text for the problem. I tried debugging it to see if my code is still running. Seems to be that it does run. I worked for hours, but I in vain and desperately NEED help.
Notes:
The Correct Answer will always be Option A (I didn't get as far as being able to get the right answer)
The Submit Button is supposed to saySubmit AND Next Question. For some reason changing the questions array length to 3 makes it not do this

public class Main2 {
public class Questions {
String Question;
String userAns;
String realAns;
}
static int count = 0;
public static void main(String[] args) {
JFrame frame = new JFrame("Screen");
frame.setSize(2500, 2500);
frame.setLayout(null);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel panel = new JPanel();
frame.getContentPane().add(panel);
panel.setSize(2500, 2500);
panel.setLayout(null);
//panel.setBackground(Color.red);
Question[] questions = new Question[3];
System.out.println(questions.length);
Question q1 = new Question();
q1.Question = "1) What is your Name?";
q1.A = "Bob";
q1.B = "Billy";
q1.C = "Joe";
q1.D = "Jill";
questions[0] = q1;
Question q2 = new Question();
q2.Question = "2) What is your Age?";
q2.A = "5";
q2.B = "69";
q2.C = "21";
q2.D = "12";
questions[1] = q2;
Question q3 = new Question();
q3.Question = "3) When Is your Birthday?";
q3.A = "May";
q3.B = "Jan";
q3.C = "Apr";
q3.D = "Aug";
questions[2] = q3;
//When this question is added the code breaks down
JLabel Question = new JLabel(questions[0].Question);
Question.setBounds(50, 0, 1500, 50);
panel.add(Question);
Question.setFont(new Font(Question.getFont().getName(), Font.PLAIN, 25));
Question.setVisible(true);
JLabel incorrectAnswerLabel = new JLabel("Incorrect Answer! Try Again");
incorrectAnswerLabel.setBounds(300, 0, 1000, 500);
panel.add(incorrectAnswerLabel);
incorrectAnswerLabel.setVisible(false);
incorrectAnswerLabel.setFont(new Font(incorrectAnswerLabel.getFont().getName(), Font.BOLD, 46));
incorrectAnswerLabel.setForeground(Color.RED);
JLabel correctAnswerLabel = new JLabel("Correct Answer! Good Job");
correctAnswerLabel.setBounds(300, 0, 1000, 500);
panel.add(correctAnswerLabel);
correctAnswerLabel.setVisible(false);
correctAnswerLabel.setFont(new Font(correctAnswerLabel.getFont().getName(), Font.BOLD, 46));
correctAnswerLabel.setForeground(Color.GREEN);
JButton submitButton = new JButton();
submitButton.setBounds(50, 250, 150, 50);
submitButton.setText("Submit");
panel.add(submitButton);
submitButton.setVisible(true);
JRadioButton OptionA = new JRadioButton(questions[0].A);
OptionA.setBounds(50, 50, 100, 50);
panel.add(OptionA);
OptionA.setVisible(true);
JRadioButton OptionB = new JRadioButton(questions[0].B);
OptionB.setBounds(50, 100, 100, 50);
panel.add(OptionB);
OptionB.setVisible(true);
JRadioButton OptionC = new JRadioButton(questions[0].C);
OptionC.setBounds(50, 150, 100, 50);
panel.add(OptionC);
OptionC.setVisible(true);
JRadioButton OptionD = new JRadioButton(questions[0].D);
OptionD.setBounds(50, 200, 100, 50);
panel.add(OptionD);
OptionD.setVisible(true);
ButtonGroup radioGroup = new ButtonGroup();
radioGroup.add(OptionA);
radioGroup.add(OptionB);
radioGroup.add(OptionC);
radioGroup.add(OptionD);
submitButton.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
if (submitButton.getText().equals("Submit")) {
if (OptionA.isSelected()) {
submitButton.setText("Next Question");
correctAnswerLabel.setVisible(true);
} else {
incorrectAnswerLabel.setVisible(true);
}
} else {
correctAnswerLabel.setVisible(false);
submitButton.setText("Submit");
if(count < questions.length-1){
count = count+1;
}
Question q = questions[count];
Question.setText(q.Question);
setAnswers(q.A, q.B, q.C, q.D, OptionA, OptionB, OptionC, OptionD);
}
}
});
}
static void setAnswers(String A, String B, String C, String D, JRadioButton a, JRadioButton b, JRadioButton c, JRadioButton d) {
List<String> answers = Arrays.asList(A, B, C, D);
Collections.shuffle(answers);
a.setText(answers.get(0));
b.setText(answers.get(1));
c.setText(answers.get(2));
d.setText(answers.get(3));
}
}

Array Index Starts from zero but the length starts from 1. The below will work if you want to add a 3rd question.
Question[] questions = new Question[3];
Arrays are not dynamic and hence if you want to add questions dynamically use an ArrayList. Otherwise increase the length of array to size you feel comfortable with.

Can't compare button icon to another icon

I am overriding the actionListener. All of the buttons besides "playbutton" have an image attached as an icon (button1, button2, button3). Every time a button is pressed, it should compare its icon to the prepared ImageIcon "livePicture" and if they are the same, it should go with the "Escaped()" method. Otherwise, the program will run the "Died()" method.
However, at least with the current code, it only uses "Died()". This, I guess, means that there is something wrong with the ifs that compare the images, but that is the only way of comparison I found on the internet.
Also, keep in mind that this is my first project, so it may seem a little cluttered.
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.border.Border;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Collections;
import java.util.Vector;
public class Frame
{
private final int WIDTH = 1024;
private final int HEIGHT = 768;
private JFrame frame;
private JPanel panel;
private JLabel human;
private JTextArea text;
private JTextArea deathMessage;
private ImageIcon livePicture;
private JButton button1;
private JButton button2;
private JButton button3;
private GridBagConstraints gbc;
private ActionListener actionListener;
private JButton playButton;
private Border border = BorderFactory.createEmptyBorder();
private Font font = new Font(Font.MONOSPACED, Font.PLAIN, 20);
public Frame()
{
Quest survival = new Quest();
actionListener = e -> {
if (e.getSource() == playButton) //playbutton works fine
{
if (!survival.IsEmpty())
{
AppendQuest(survival.GetQuest());
survival.RemoveQuest();
}
else
{
Escaped();
}
}
else if (e.getSource() == button1) //button1 action
{
if (button1.getIcon().toString() != livePicture.toString())
{
Died();
}
else
{
if (!survival.IsEmpty())
{
AppendQuest(survival.GetQuest());
survival.RemoveQuest();
}
else
{
Escaped();
}
}
}
else if (e.getSource() == button2) //button2 action
{
if (button2.getIcon().toString() != livePicture.toString())
{
Died();
}
else
{
if (!survival.IsEmpty())
{
AppendQuest(survival.GetQuest());
survival.RemoveQuest();
}
else
{
Escaped();
}
}
}
else if (e.getSource() == button3) //button3 action
{
if (button3.getIcon().toString() != livePicture.toString())
{
Died();
}
else
{
if (!survival.IsEmpty())
{
AppendQuest(survival.GetQuest());
survival.RemoveQuest();
}
else
{
Escaped();
}
}
}
};
//I left the rest of the constructor for bonus info
frame = new JFrame();
panel = new JPanel();
gbc = new GridBagConstraints();
human = new JLabel(ImageSize(200, 200, "res/human.png"));
text = new JTextArea("You have lost in the forest. Now you have to find " +
"your way back.");
FormatText(text);
deathMessage = new JTextArea();
frame.setTitle("Shady Path");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(WIDTH, HEIGHT);
frame.setLocationRelativeTo(null);
frame.getContentPane().setBackground(Color.BLACK);
frame.setResizable(false);
playButton = new JButton();
playButton.addActionListener(actionListener);
playButton.setFont(font);
playButton.setText("Play");
playButton.setForeground(Color.WHITE);
playButton.setBackground(Color.BLACK);
playButton.setBorder(border);
panel.setLayout(new GridBagLayout());
panel.setOpaque(false);
gbc.anchor = GridBagConstraints.PAGE_START;
gbc.gridwidth = GridBagConstraints.REMAINDER;
panel.add(human, gbc);
gbc.insets = new Insets(30, 0, 0, 0);
gbc.weightx = 1;
gbc.fill = GridBagConstraints.HORIZONTAL;
panel.add(text, gbc);
gbc.fill = GridBagConstraints.VERTICAL;
gbc.insets = new Insets(50, 0, 68, 0);
panel.add(playButton, gbc);
frame.add(panel);
frame.setVisible(true);
}
public void AppendQuest(Vector<String> event)
{
panel.removeAll();
panel.add(human, gbc);
gbc.insets = new Insets(0, 0, 30, 0);
text.setText(event.remove(0));
FormatText(text);
panel.add(text, gbc);
deathMessage.setText(event.remove(0));
FormatText(deathMessage);
livePicture = ImageSize(50, 50, event.remove(0));
Collections.shuffle(event);
ImageIcon picture1 = ImageSize(50, 50, event.get(0)); //setting button1
button1 = new JButton();
button1.addActionListener(actionListener);
button1.setIcon(picture1);
button1.setBorder(border);
ImageIcon picture2 = ImageSize(50, 50, event.get(1)); //setting button2
button2 = new JButton();
button2.addActionListener(actionListener);
button2.setIcon(picture2);
button2.setBorder(border);
ImageIcon picture3 = ImageSize(50, 50, event.get(2)); //setting button3
button3 = new JButton();
button3.addActionListener(actionListener);
button3.setIcon(picture3);
button3.setBorder(border);
gbc.gridwidth = GridBagConstraints.HORIZONTAL;
gbc.insets = new Insets(50, 360, 100, 0);
panel.add(button1, gbc);
gbc.insets = new Insets(50, 77, 100, 77);
panel.add(button2, gbc);
gbc.insets = new Insets(50, 0, 100, 360);
panel.add(button3, gbc);
panel.revalidate();
panel.repaint();
}
private void Escaped()
{
//Unnecessary info
}
private void Died()
{
//Unnecessary info
}
//This just resizes the images
private ImageIcon ImageSize(int x, int y, String fileName)
{
BufferedImage baseImg = null;
try {
baseImg = ImageIO.read(new File(fileName));
} catch (IOException e) {
e.printStackTrace();
}
Image resizedImg = baseImg.getScaledInstance(x, y, Image.SCALE_SMOOTH);
ImageIcon IconImg = new ImageIcon(resizedImg);
return IconImg;
}
private void FormatText(JTextArea baseText)
{
//Unnecessary info
}
}
EDIT:
Here is also an example of what vector could go as an "event" in "AppendQuest"
Vector<String> items2 = new Vector<>();
items2.add("You are kind of disoriented. What will you use to find the right way?" +
" moss, sun or tree barks");
items2.add("Unfortunately you didn't orient yourself well enough. Now, you " +
"will roam through the forest forever.");
items2.add("res/orientation_sun.png");
items2.add("res/orientation_moss.png");
items2.add("res/orientation_sun.png");
items2.add("res/orientation_tree_bark.png");

You can compare Objects with the .equals(Object) function:
if(!button.getIcon().equals(livePicture))
{
Died();
}
else
{...}
The == operator checks the identity of objects or the value of native types (e.g. int).
That means:
int nr1 = 1;
int nr2 = 1;
if(nr1 == nr2) {...} //true -> int is a native type
String str1 = "test";
String str2 = "test";
if(str1 == str2) {...} //false -> Same content but not same objects
if(str1.equals(str2)) {...} //true -> Same content, different objects
//Edit:
Another problem might be that you remove the image-url from your vector while creating the livePicture:
livePicture = ImageSize(50, 50, event.remove(0));
The url is not in the list anymore when you create your buttons. The result is that the buttons will never have the same image as your livePicture has, unless you're changing it (do you?).

Having trouble calling a JPanel from a different class

Im trying to create a Hangman game for my java class and im struggling with how to make each class work together. In this case, Im trying to write my phrase in from the selectPhrase method to the mainPanel. Im very new to programming so any help would be very appreciated.
Thank you
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
/**
* Created by Alex on 4/22/2016.
*/
``public class HangmanGame extends JFrame implements ActionListener {
public HangmanGame() {
JPanel lettersPanel = new JPanel(new GridLayout(5,8,5,5));
JButton jbtA = new JButton("A");
JButton jbtB = new JButton("B");
JButton jbtC = new JButton("C");
JButton jbtD = new JButton("D");
JButton jbtE = new JButton("E");
JButton jbtF = new JButton("F");
JButton jbtG = new JButton("G");
JButton jbtH = new JButton("H");
JButton jbtI = new JButton("I");
JButton jbtJ = new JButton("J");
JButton jbtK = new JButton("K");
JButton jbtL = new JButton("L");
JButton jbtM = new JButton("M");
JButton jbtN = new JButton("N");
JButton jbtO = new JButton("O");
JButton jbtP = new JButton("P");
JButton jbtQ = new JButton("Q");
JButton jbtR = new JButton("R");
JButton jbtS = new JButton("S");
JButton jbtT = new JButton("T");
JButton jbtU = new JButton("U");
JButton jbtV = new JButton("V");
JButton jbtW = new JButton("W");
JButton jbtX = new JButton("X");
JButton jbtY = new JButton("Y");
JButton jbtZ = new JButton("Z");
lettersPanel.add(jbtA);
lettersPanel.add(jbtB);
lettersPanel.add(jbtC);
lettersPanel.add(jbtD);
lettersPanel.add(jbtE);
lettersPanel.add(jbtF);
lettersPanel.add(jbtG);
lettersPanel.add(jbtH);
lettersPanel.add(jbtI);
lettersPanel.add(jbtJ);
lettersPanel.add(jbtK);
lettersPanel.add(jbtL);
lettersPanel.add(jbtM);
lettersPanel.add(jbtN);
lettersPanel.add(jbtO);
lettersPanel.add(jbtP);
lettersPanel.add(jbtQ);
lettersPanel.add(jbtR);
lettersPanel.add(jbtS);
lettersPanel.add(jbtT);
lettersPanel.add(jbtU);
lettersPanel.add(jbtV);
lettersPanel.add(jbtW);
lettersPanel.add(jbtX);
lettersPanel.add(jbtY);
lettersPanel.add(jbtZ);
JPanel mainPanel = new JPanel(new BorderLayout());
setLayout(new GridLayout(2,2,5,5));
mainPanel.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
mainPanel.add(lettersPanel, BorderLayout.EAST);
mainPanel.setBackground(Color.BLACK);
//mainPanel.add()
add(mainPanel, BorderLayout.CENTER);
}
public static void main(String[] args) {
JFrame frame = new HangmanGame();
frame.add(new HangmanGraphics());
frame.setTitle("Hangman");
frame.setSize(1020, 800);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
frame.setResizable(false);
}
static String selectPhrase()
{
String currentGuess = "*";
int[] previousValues = new int[5];
int totalRounds = 0;
//set isValid equal to false and creates a random number between 1 and 6
//(between 1 and 6 because previousValues is used to store the old numbers,
//and if between 0 and 5 were used, 0 would trip every time because an uninitialized
//array has 0's (null) in every position)
boolean isValid = false;
int index = (int)(Math.random() * 5 + 1);
//enters loop because isValid is false, so !isValid is true
while(!isValid)
{
//sets isValid equal to true, so if it never gets changed during the loop, it will exit next time around
isValid = true;
for(int i = 0; i < totalRounds; i++)
{
//if the randomly generated value is one of the previous ones, make isValid false
if(index == previousValues[i])
{
isValid = false;
}
}
//if isValid is false, create a new random number between 1 and 6
if(!isValid)
{
index = (int)(Math.random() * 5 + 1);
}
}
//once a value that's never been used before is created, save it in previousValues
//so that it is not used again
previousValues[totalRounds] = index;
totalRounds++;
//return phrase at the index of the random number
String[] phrase = {"NULL", "Go Team", "Hello World" , "Java Rocks", "Bread Bowl" , "Soup"};
return phrase[index];
for( int i=0; i<phrase.length; i++) {
currentGuess = currentGuess.concat("?");
}
.setText( currentGuess );
}
#Override
public void actionPerformed(ActionEvent e) {
}
}
class HangmanGraphics extends JPanel {
JPanel graphicsPanel = new JPanel();
int incorrectGuesses =0;
#Override
public void paintComponent(Graphics g){
super.paintComponent(g);
Graphics2D g2D = (Graphics2D) g;
BasicStroke aStroke = new BasicStroke(15.0f, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND);
g2D.setStroke(aStroke);
g2D.setColor(Color.BLUE);
switch (incorrectGuesses) {
case 10:
g2D.drawLine(200, 200, 150, 250); // Left leg
case 9:
g2D.drawLine(200, 200, 250, 250); // Right leg
case 8:
g2D.drawLine(150, 150, 200, 175); // Left arm
case 7:
g2D.drawLine(250, 150, 200, 175); // Right arm
case 6:
g2D.drawLine(200, 200, 200, 150); // Torso
case 5:
g2D.drawOval(175, 100, 50, 50); // Head
case 4:
g2D.drawLine(200, 100, 200, 50);// Noose
case 3:
g2D.drawLine(200, 50, 100, 50);//Plank
case 2:
g2D.drawLine(100, 300, 100, 50); //Post
case 1:
g2D.drawLine(20, 300, 300, 300); //Stage
}
repaint();
graphicsPanel.add(new HangmanGraphics());
}
}

Your issue, which is common to many if not most new developers, is the over use of static and a lack of understanding of Object Oriented Programming, and how to use objects. In your case, you are trying to create a main method inside a JFrame type object (HangmanGame) and then you have a static method you want to call, typically because you are trying to figure out how to call it from the static main method. You are better off creating a separate 'driver' class for HangManGame, that contains the main method. The HangManGame class then creates an instance of a HangManFrame (calls new HangManFrame()).
The 2 important points to remember are:
1) In your main method, create an instance of the class that the main is defined in, then call methods on that object. By doing that, you don't need to declare a bunch of static methods and will avoid a lot of pain like you are experiencing now. For example, here is a definition of the HangManGame class:
package hangman;
public class HangManGame {
HangManFrame frame;
public HangManGame(){
frame = new HangManFrame();
}
public void play() {
frame.setVisible(true);
String selectedPhrase = selectPhrase();
System.out.println("Selected phrase: " + selectedPhrase);
}
public String selectPhrase() {
String currentGuess = "*";
int[] previousValues = new int[5];
int totalRounds = 0;
//set isValid equal to false and creates a random number between 1 and 6
//(between 1 and 6 because previousValues is used to store the old numbers,
//and if between 0 and 5 were used, 0 would trip every time because an uninitialized
//array has 0's (null) in every position)
boolean isValid = false;
int index = (int)(Math.random() * 5 + 1);
//enters loop because isValid is false, so !isValid is true
while(!isValid)
{
//sets isValid equal to true, so if it never gets changed during the loop, it will exit next time around
isValid = true;
for(int i = 0; i < totalRounds; i++)
{
//if the randomly generated value is one of the previous ones, make isValid false
if(index == previousValues[i])
{
isValid = false;
}
}
//if isValid is false, create a new random number between 1 and 6
if(!isValid)
{
index = (int)(Math.random() * 5 + 1);
}
}
//once a value that's never been used before is created, save it in previousValues
//so that it is not used again
previousValues[totalRounds] = index;
totalRounds++;
//return phrase at the index of the random number
String[] phrase = {"NULL", "Go Team", "Hello World" , "Java Rocks", "Bread Bowl" , "Soup"};
return phrase[index];
}
public static void main(String[] args) {
HangManGame game = new HangManGame();
game.play();
}
}
Notice that the only task the main method performs is to create an instance of the HangManGame class and call the play() method on that object..that's it!
Also notice that the selectPhrase() method is not declared static, as it is not necessary.
2) For all your classes, objects that you need access to and need to be able to call methods on should be declared outside of methods as 'class-wide instance variables'. For example, notice how the HangManFrame is declared inside the HangManGame class, but outside of the methods. Then the frame is created and assigned inside the constructor for `HangManGame
public class HangManGame {
HangManFrame frame;
public HangManGame(){
frame = new HangManFrame();
}
...
}
Doing this will allow you to call methods on the frame from within any of the HangManGame methods.
I have slightly refactored your HangManFrame and HangManGraphics class, following similar stategies, included below.
Finally, you should begin to create other methods on the HangManGame class, maybe like nextMove(), or updateBoard() or whatever, that are driven by and called from the play() method.
HangManFrame class:
package hangman;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class HangManFrame extends JFrame implements ActionListener {
JPanel lettersPanel;
public HangManFrame() {
lettersPanel = new JPanel(new GridLayout(5, 8, 5, 5));
JButton jbtA = new JButton("A");
JButton jbtB = new JButton("B");
JButton jbtC = new JButton("C");
JButton jbtD = new JButton("D");
JButton jbtE = new JButton("E");
JButton jbtF = new JButton("F");
JButton jbtG = new JButton("G");
JButton jbtH = new JButton("H");
JButton jbtI = new JButton("I");
JButton jbtJ = new JButton("J");
JButton jbtK = new JButton("K");
JButton jbtL = new JButton("L");
JButton jbtM = new JButton("M");
JButton jbtN = new JButton("N");
JButton jbtO = new JButton("O");
JButton jbtP = new JButton("P");
JButton jbtQ = new JButton("Q");
JButton jbtR = new JButton("R");
JButton jbtS = new JButton("S");
JButton jbtT = new JButton("T");
JButton jbtU = new JButton("U");
JButton jbtV = new JButton("V");
JButton jbtW = new JButton("W");
JButton jbtX = new JButton("X");
JButton jbtY = new JButton("Y");
JButton jbtZ = new JButton("Z");
lettersPanel.add(jbtA);
lettersPanel.add(jbtB);
lettersPanel.add(jbtC);
lettersPanel.add(jbtD);
lettersPanel.add(jbtE);
lettersPanel.add(jbtF);
lettersPanel.add(jbtG);
lettersPanel.add(jbtH);
lettersPanel.add(jbtI);
lettersPanel.add(jbtJ);
lettersPanel.add(jbtK);
lettersPanel.add(jbtL);
lettersPanel.add(jbtM);
lettersPanel.add(jbtN);
lettersPanel.add(jbtO);
lettersPanel.add(jbtP);
lettersPanel.add(jbtQ);
lettersPanel.add(jbtR);
lettersPanel.add(jbtS);
lettersPanel.add(jbtT);
lettersPanel.add(jbtU);
lettersPanel.add(jbtV);
lettersPanel.add(jbtW);
lettersPanel.add(jbtX);
lettersPanel.add(jbtY);
lettersPanel.add(jbtZ);
JPanel mainPanel = new JPanel(new BorderLayout());
setLayout(new GridLayout(2, 2, 5, 5));
mainPanel.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
mainPanel.add(lettersPanel, BorderLayout.EAST);
mainPanel.setBackground(Color.BLACK);
add(mainPanel, BorderLayout.CENTER);
add(new HangmanGraphics());
setTitle("Hangman");
setSize(1020, 800);
setLocationRelativeTo(null);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setResizable(false);
}
#Override
public void actionPerformed(ActionEvent e) {
System.out.println("Received actionPerformed event: " + e.getActionCommand());
}
}
HangManGraphics class:
package hangman;
import javax.swing.;
import java.awt.;
class HangmanGraphics extends JPanel {
JPanel graphicsPanel = new JPanel();
int incorrectGuesses =0;
#Override
public void paintComponent(Graphics g){
super.paintComponent(g);
Graphics2D g2D = (Graphics2D) g;
BasicStroke aStroke = new BasicStroke(15.0f, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND);
g2D.setStroke(aStroke);
g2D.setColor(Color.BLUE);
switch (incorrectGuesses) {
case 10:
g2D.drawLine(200, 200, 150, 250); // Left leg
case 9:
g2D.drawLine(200, 200, 250, 250); // Right leg
case 8:
g2D.drawLine(150, 150, 200, 175); // Left arm
case 7:
g2D.drawLine(250, 150, 200, 175); // Right arm
case 6:
g2D.drawLine(200, 200, 200, 150); // Torso
case 5:
g2D.drawOval(175, 100, 50, 50); // Head
case 4:
g2D.drawLine(200, 100, 200, 50);// Noose
case 3:
g2D.drawLine(200, 50, 100, 50);//Plank
case 2:
g2D.drawLine(100, 300, 100, 50); //Post
case 1:
g2D.drawLine(20, 300, 300, 300); //Stage
}
repaint();
graphicsPanel.add(new HangmanGraphics());
}
}