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is the method to create simple login wrong

I am a newbie in Java GUI development and I am stuck in the following code.
I am open to suggestions. I am actually trying to create a simple login that gives OK if the password is matched to the number 3124, and otherwise shows the error message. Please help me.
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JTextField;
public class testing {
private JFrame frame;
private JTextField username;
private JTextField password;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
testing window = new testing();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public testing() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
JButton btnNewButton_1 = new JButton("cancel");
btnNewButton_1.setBounds(266, 181, 109, 56);
frame.getContentPane().add(btnNewButton_1);
username = new JTextField();
username.setBounds(227, 11, 128, 39);
frame.getContentPane().add(username);
username.setColumns(10);
password = new JTextField();
password.setBounds(227, 76, 128, 39);
frame.getContentPane().add(password);
final int num;
num=Integer.parseInt(password);
password.setColumns(10);
JButton btnNewButton = new JButton("login");
btnNewButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if(num==3124)
{JOptionPane.showMessageDialog(null, "correct");}
else
{JOptionPane.showMessageDialog(null, "wrong");}
}
});
btnNewButton.setBounds(62, 181, 123, 56);
frame.getContentPane().add(btnNewButton);
}
}

You were checking the password even before the user has had the chance to enter anything into the text box. You need to get and check the value of num in the event listener code i.e. in actionPerformed. Also, don't convert the password to int (someone may enter some non-numeric string).
This code below works better.
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import javax.swing.JTextField;
public class Testing {
private JFrame frame;
private JTextField username;
private JTextField password;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Testing window = new Testing();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public Testing() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
JButton btnNewButton_1 = new JButton("cancel");
btnNewButton_1.setBounds(266, 181, 109, 56);
frame.getContentPane().add(btnNewButton_1);
username = new JTextField();
username.setBounds(227, 11, 128, 39);
frame.getContentPane().add(username);
username.setColumns(10);
password = new JTextField();
password.setBounds(227, 76, 128, 39);
frame.getContentPane().add(password);
password.setColumns(10);
JButton btnNewButton = new JButton("login");
btnNewButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
final String num;
num = (password.getText());
if (num.equalsIgnoreCase("3124")) {
JOptionPane.showMessageDialog(null, "correct");
} else {
JOptionPane.showMessageDialog(null, "wrong");
}
}
});
btnNewButton.setBounds(62, 181, 123, 56);
frame.getContentPane().add(btnNewButton);
}
}

Setting a JLabel visible on JRadioButton click

I tried setting JLabel to being visible only after I select a certain JRadioButton. The program is getting an error if I set lblNewLabel_1.setVisible(true) in the action performed of a radio button. It worked with the text field, but with this not. What can I do? Is it different with the label? Is there any advice someone can offer me?
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.Window;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JTextArea;
import javax.swing.JRadioButton;
import javax.swing.JLabel;
import java.awt.Font;
import javax.swing.JTextField;
import javax.swing.ButtonGroup;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class Fereastra extends JFrame {
private JPanel contentPane;
private JTextField textField;
private JTextField textField_1;
private final ButtonGroup buttonGroup = new ButtonGroup();
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Fereastra frame = new Fereastra();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public Fereastra() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 751, 565);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
contentPane.setLayout(null);
setContentPane(contentPane);
JTextArea textArea = new JTextArea();
textArea.setBounds(12, 13, 447, 251);
contentPane.add(textArea);
JRadioButton rdbtnNewRadioButton = new JRadioButton("Cautarea pe nivel");
rdbtnNewRadioButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if(rdbtnNewRadioButton.isSelected())
{
textField.setVisible(false);
textField_1.setVisible(false);
}
}
});
buttonGroup.add(rdbtnNewRadioButton);
rdbtnNewRadioButton.setBounds(488, 55, 185, 25);
contentPane.add(rdbtnNewRadioButton);
JRadioButton rdbtnNewRadioButton_1 = new JRadioButton("Cautarea in adancime");
rdbtnNewRadioButton_1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
if(rdbtnNewRadioButton_1.isSelected())
{
textField.setVisible(true);
textField_1.setVisible(true);
}
else
{
textField.setVisible(false);
textField_1.setVisible(false);
}
}
});
buttonGroup.add(rdbtnNewRadioButton_1);
rdbtnNewRadioButton_1.setBounds(488, 96, 237, 25);
contentPane.add(rdbtnNewRadioButton_1);
JRadioButton rdbtnNewRadioButton_2 = new JRadioButton("Costul uniform");
rdbtnNewRadioButton_2.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if(rdbtnNewRadioButton_2.isSelected())
{
textField.setVisible(false);
textField_1.setVisible(false);
}
}
});
buttonGroup.add(rdbtnNewRadioButton_2);
rdbtnNewRadioButton_2.setBounds(488, 138, 127, 25);
contentPane.add(rdbtnNewRadioButton_2);
JRadioButton rdbtnNewRadioButton_3 = new JRadioButton("Adancime iterativa");
rdbtnNewRadioButton_3.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if(rdbtnNewRadioButton_3.isSelected())
{
textField_1.setVisible(true);
textField.setVisible(true);
}
else
{
textField_1.setVisible(false);
textField.setVisible(false);
}
}
});
buttonGroup.add(rdbtnNewRadioButton_3);
rdbtnNewRadioButton_3.setBounds(488, 179, 237, 25);
contentPane.add(rdbtnNewRadioButton_3);
JRadioButton rdbtnNewRadioButton_4 = new JRadioButton("Greedy");
rdbtnNewRadioButton_4.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if(rdbtnNewRadioButton_4.isSelected())
{
textField.setVisible(false);
textField_1.setVisible(false);
}
}
});
buttonGroup.add(rdbtnNewRadioButton_4);
rdbtnNewRadioButton_4.setBounds(488, 221, 127, 25);
contentPane.add(rdbtnNewRadioButton_4);
JLabel lblNewLabel = new JLabel("Alegeti:");
lblNewLabel.setFont(new Font("Tahoma", Font.PLAIN, 16));
lblNewLabel.setBounds(488, 13, 84, 33);
contentPane.add(lblNewLabel);
textField = new JTextField();
textField.setBounds(402, 277, 116, 22);
contentPane.add(textField);
textField.setColumns(10);
textField.setVisible(false);
textField_1 = new JTextField();
textField_1.setBounds(246, 277, 116, 22);
contentPane.add(textField_1);
textField_1.setColumns(10);
textField_1.setVisible(false);
JLabel lblNewLabel_1 = new JLabel("Introduceti valorile dorite:");
lblNewLabel_1.setFont(new Font("Tahoma", Font.PLAIN, 16));
lblNewLabel_1.setBounds(22, 277, 212, 21);
contentPane.add(lblNewLabel_1);
lblNewLabel_1.setVisible(false);
}
}

It's because your label is declared in function context, put the declaration next the textbox declaration and it should work fine

How to store string or integer in java.swing JTextField?

Hello I am working on this project to store student names and record their grades. I have the entire program mapped out and all I need to do now is record the integers and strings from the user input and call it from different classes. I am having trouble with this. Do I use an array? How do I call from another class? Thank you.
package gradebook;
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.util.Scanner;
import java.awt.event.ActionEvent;
import javax.swing.JTextArea;
public class Student extends JFrame {
private JFrame studentFrame;
private JPanel contentPane;
private JTextField studentNameTextField;
protected Component frame;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Student frame = new Student();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public Student() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
JLabel gradebookLabel = new JLabel("Gradebook");
gradebookLabel.setBounds(189, 6, 68, 16);
contentPane.add(gradebookLabel);
JLabel lblPleaseEnterThe = new JLabel("Please enter the student name");
lblPleaseEnterThe.setBounds(130, 105, 194, 16);
contentPane.add(lblPleaseEnterThe);
studentNameTextField = new JTextField("Enter here");
String stdname = studentNameTextField.getText();
studentNameTextField.setBounds(130, 133, 194, 26);
contentPane.add(studentNameTextField);
studentNameTextField.setColumns(10);
JButton continueButton = new JButton("Continue");
continueButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent a) {
if(continueButton.isEnabled()){
Student.this.dispose();
Student studentScreen = new Student();
studentScreen.dispose();
AddGrades addGradesScreen = new AddGrades();
addGradesScreen.setVisible(true);
}
}
});
continueButton.setBounds(327, 243, 117, 29);
contentPane.add(continueButton);
JButton cancelButton = new JButton("Cancel");
cancelButton.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent a) {
if(cancelButton.isEnabled()){
MainScreen mainScreenScreen = new MainScreen();
mainScreenScreen.setVisible(true);
contentPane.setVisible(false);
contentPane.disable();
}
}
});
cancelButton.setBounds(207, 243, 117, 29);
contentPane.add(cancelButton);
}
private void initizalize() {
// TODO Auto-generated method stub
}
}
Is it something along the lines of this?
studentNameTextField = new JTextField("Enter here");
String stdname = studentNameTextField.getText();
I know this would be storing it but how do I call that in a different class so I can make it appear on a different Frame?
Update: Okay so I've done this
Student frame = new Student();
String stdname = frame.studentNameTextField.getText();
JLabel addgradesLabel = new JLabel("Add grades for" + frame.studentNameTextField);
addgradesLabel.setBounds(139, 34, 167, 29);
contentPane.add(addgradesLabel);
And it's still not working. I believe I'm not implementing this correctly. I'm trying to title the label with what the user inputs for the name. So it would but "Add grades for" + stdname But it's not calling it correctly. How can I fix this?
Here is my code from the AddStudentName class
studentNameTextField = new JTextField();
studentNameTextField.setBounds(130, 133, 194, 26);
contentPane.add(studentNameTextField);
studentNameTextField.setColumns(10);
JButton continueButton = new JButton("Continue");
continueButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent a) {
if(continueButton.isEnabled()){
Student.this.dispose();
Student studentScreen = new Student();
studentScreen.dispose();
AddGrades addGradesScreen = new AddGrades();
addGradesScreen.setVisible(true);
}
}
});
What should I add here to save the input that the user is inputting into the JTextField? Thanks for the help
Here's the full code for the classes:
package gradebook;
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.util.Scanner;
import java.awt.event.ActionEvent;
import javax.swing.JTextArea;
public class Student extends JFrame {
private JFrame studentFrame;
private JPanel contentPane;
public JTextField studentNameTextField;
protected Component frame;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Student frame = new Student();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public Student() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
JLabel gradebookLabel = new JLabel("Gradebook");
gradebookLabel.setBounds(189, 6, 68, 16);
contentPane.add(gradebookLabel);
JLabel lblPleaseEnterThe = new JLabel("Please enter the student name");
lblPleaseEnterThe.setBounds(130, 105, 194, 16);
contentPane.add(lblPleaseEnterThe);
JTextField studentNameTextField = new JTextField();
studentNameTextField.setBounds(130, 133, 194, 26);
contentPane.add(studentNameTextField);
studentNameTextField.setColumns(10);
JButton continueButton = new JButton("Continue");
continueButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent a) {
if(continueButton.isEnabled()){
Student studentScreen = new Student();
studentScreen.dispose();
AddGrades addGradesScreen = new AddGrades();
addGradesScreen.setVisible(true);
}
}
});
continueButton.setBounds(327, 243, 117, 29);
contentPane.add(continueButton);
JButton cancelButton = new JButton("Cancel");
cancelButton.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent a) {
if(cancelButton.isEnabled()){
MainScreen mainScreenScreen = new MainScreen();
mainScreenScreen.setVisible(true);
contentPane.setVisible(false);
contentPane.disable();
}
}
});
cancelButton.setBounds(207, 243, 117, 29);
contentPane.add(cancelButton);
}
private void initizalize() {
// TODO Auto-generated method stub
}
}
and:
package gradebook;
import java.awt.BorderLayout;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class AddGrades extends JFrame {
private JPanel contentPane;
private JTextField Assignment1;
private JTextField Assignment2;
private JTextField Assignment3;
private JTextField Assignment4;
private JLabel testsLabel;
private JTextField Test1;
private JTextField Test2;
public JTextField Test3;
public JTextField Test4;
/**
* Launch the application.
*/
public JFrame frame;
public JButton continueButton;
public JButton exitButton;
public static void main(String[] args) {
AddGrades frame = new AddGrades();
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
AddGrades frame = new AddGrades();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the frame.
*/
public AddGrades() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
JLabel gradebookLabel = new JLabel("Gradebook");
gradebookLabel.setBounds(189, 6, 68, 16);
contentPane.add(gradebookLabel);
JLabel addgradesLabel = new JLabel("Add grades for" + stdname);
addgradesLabel.setBounds(139, 34, 167, 29);
contentPane.add(addgradesLabel);
JLabel assignmentsLabel = new JLabel("Assignments:");
assignmentsLabel.setBounds(19, 75, 86, 16);
contentPane.add(assignmentsLabel);
Assignment1 = new JTextField();
Assignment1.setBounds(54, 91, 130, 26);
contentPane.add(Assignment1);
Assignment1.setColumns(10);
Assignment2 = new JTextField();
Assignment2.setBounds(54, 129, 130, 26);
contentPane.add(Assignment2);
Assignment2.setColumns(10);
Assignment3 = new JTextField();
Assignment3.setBounds(54, 167, 130, 26);
contentPane.add(Assignment3);
Assignment3.setColumns(10);
Assignment4 = new JTextField();
Assignment4.setBounds(54, 205, 130, 26);
contentPane.add(Assignment4);
Assignment4.setColumns(10);
testsLabel = new JLabel("Tests:");
testsLabel.setBounds(243, 75, 38, 16);
contentPane.add(testsLabel);
Test1 = new JTextField();
Test1.setBounds(262, 91, 130, 26);
contentPane.add(Test1);
Test1.setColumns(10);
Test2 = new JTextField();
Test2.setBounds(262, 129, 130, 26);
contentPane.add(Test2);
Test2.setColumns(10);
Test3 = new JTextField();
Test3.setBounds(262, 167, 130, 26);
contentPane.add(Test3);
Test3.setColumns(10);
Test4 = new JTextField();
Test4.setBounds(262, 205, 130, 26);
contentPane.add(Test4);
Test4.setColumns(10);
continueButton = new JButton("Continue");
continueButton.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent a){
if (continueButton.isEnabled()){
MainScreen mainScreenScreen = new MainScreen();
mainScreenScreen.setVisible(true);
}
}
});
continueButton.setBounds(327, 243, 117, 29);
contentPane.add(continueButton);
exitButton = new JButton("Exit");
exitButton.setBounds(208, 243, 117, 29);
contentPane.add(exitButton);
}
}
I'm trying to take the input from the JTextField
JTextField studentNameTextField = new JTextField();
and set it on the label
JLabel addgradesLabel = new JLabel("Add grades for" + stdname);
Where stdname would be the user input from the JTextField.
Now I'm getting errors from
public static void main(String[] args) {
AddGrades frame = new AddGrades();
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
AddGrades frame = new AddGrades();
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
AddGrades frame = new AddGrades(); gives me error Add argument to match AddGrades(String)
The constructor AddGrades() is undefined

Edit: The best way to do this is to pass an argument to your newly created AddGrades class. See below:
public AddGrades(String stdname) {
JLabel addgradesLabel = new JLabel("Add grades for " + stdname);
}
You will need to modify your code to pass a string to your AddGrades class wherever you create it:
JButton continueButton = new JButton("Continue");
continueButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent a) {
if(continueButton.isEnabled()){
Student studentScreen = new Student();
studentScreen.dispose();
AddGrades addGradesScreen = new AddGrades(studentNameTextField.getText());
addGradesScreen.setVisible(true);
}
}
});
That worked for me - I downloaded your code and tested it.

JSpinner or JFormattedTextField would be my first thought, but if you can't do that then you could use Integer.parseInt to parse a String to int and a NumberFormat to format the numbers to Strings
Maybe have a look at How to Use Spinners and How to Use Formatted Text Fields for starters
I know this would be storing it but how do I call that in a different class so I can make it appear on a different JFrame?
That's a open question with little context. You might use some kind of "model" which represented one or more Student values; you might use a Observer Pattern to allow the editor to generate events to interested parties which would tell them that something has changed; you might use a Model-View-Controller; you might use a modal dialog and when it's closed, ask the editor for the values via getters.
Have a look at How to Make Dialogs for more details
One of things you want to keep in mind is "responsibility" and "encapsulation". You don't want outside parties to have uncontrolled access into your editor or model, this could allow them to modify the state in an uncontrolled way leading to inconsistencies in your data or UI.
You need to decide who is actually responsible for modifying the state of the model. There's no "right" answer, for example, you could have the editor either be capable of editing existing student objects or creating new ones based on how it's configured, equally, you could also have the editor be "dumb" and simply use setters to setup the editor and getters to get the values.
There are lots of options available to you, which you would use would be based on the context in which you want to use it. My gut feeling is start with an observer pattern and a modal dialog.

How to connect two frames in Java?

I have three different frames:
welcome.java
Register.java
LoginForm.java
If I click on Login button login page must open(i.e LoginForm.java) and if I click on Register button register page must open
//welcome.java
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import javax.swing.JLabel;
public class welcome extends JFrame
{
private JFrame frame;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
welcome window = new welcome();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public welcome() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
JButton btnLogIn = new JButton("LOG IN");
btnLogIn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
}
});
btnLogIn.setBounds(200, 69, 117, 25);
frame.getContentPane().add(btnLogIn);
JButton btnRegister = new JButton("Register");
btnRegister.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
}
});
btnRegister.setBounds(200, 138, 117, 25);
frame.getContentPane().add(btnRegister);
JLabel lblNewToSvk = new JLabel("New to SVK Polytechnic ?");
lblNewToSvk.setBounds(12, 143, 191, 15);
frame.getContentPane().add(lblNewToSvk);
}
}
.
`//LoginForm.java
import java.awt.EventQueue;
import javax.swing.JScrollPane;
public class LoginForm extends JPanel implements ItemListener
{
/**
*
*/
private static final long serialVersionUID = 1L;
private JFrame frame;
private JTextField textField;
private JPasswordField pwdJjh;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
LoginForm window = new LoginForm();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public LoginForm() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
JLabel lblStudentLogin = new JLabel("Login ");
lblStudentLogin.setFont(new Font("Dialog", Font.BOLD | Font.ITALIC, 30));
lblStudentLogin.setHorizontalAlignment(SwingConstants.CENTER);
lblStudentLogin.setBounds(94, 12, 265, 36);
frame.getContentPane().add(lblStudentLogin);
JLabel lblUserName = new JLabel("USER NAME");
lblUserName.setFont(new Font("Dialog", Font.BOLD, 15));
lblUserName.setBounds(12, 74, 111, 15);
frame.getContentPane().add(lblUserName);
textField = new JTextField();
textField.setFont(new Font("Dialog", Font.PLAIN, 15));
textField.setBounds(141, 70, 160, 22);
frame.getContentPane().add(textField);
textField.setColumns(10);
JLabel lblPassword = new JLabel("PASSWORD");
lblPassword.setFont(new Font("Dialog", Font.BOLD, 15));
lblPassword.setBounds(12, 116, 111, 15);
frame.getContentPane().add(lblPassword);
pwdJjh = new JPasswordField();
pwdJjh.setFont(new Font("Dialog", Font.PLAIN, 15));
pwdJjh.setBounds(141, 114, 160, 22);
frame.getContentPane().add(pwdJjh);
JLabel lblUserType = new JLabel("USER TYPE");
lblUserType.setFont(new Font("Dialog", Font.BOLD, 15));
lblUserType.setBounds(12, 154, 111, 15);
frame.getContentPane().add(lblUserType);
JComboBox<String> cm = new JComboBox<String>();
cm.setBounds(141, 148, 160, 24);
cm.addItem("User");
cm.addItem("Admin");
cm.addItemListener(this);
setLayout(null);
frame.getContentPane().add(cm);
JButton btnLogin = new JButton("Login ");
btnLogin.setBounds(41, 199, 117, 25);
frame.getContentPane().add(btnLogin);
JButton btnCancle = new JButton("Cancel");
btnCancle.setBounds(209, 199, 117, 25);
frame.getContentPane().add(btnCancle);
}
#Override
public void itemStateChanged(ItemEvent arg0) {
// TODO Auto-generated method stub
}
}
.
//Register.java
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JLabel;
import java.awt.Font;
import java.awt.Color;
import javax.swing.JComboBox;
import javax.swing.DefaultComboBoxModel;
public class Register {
private JFrame frame;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Register window = new Register();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public Register() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame();
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
JLabel lblRegisterForm = new JLabel("Register Form");
lblRegisterForm.setForeground(Color.BLUE);
lblRegisterForm.setFont(new Font("Dialog", Font.BOLD | Font.ITALIC, 25));
lblRegisterForm.setBounds(119, 12, 209, 25);
frame.getContentPane().add(lblRegisterForm);
JLabel lblSelectTheUser = new JLabel("Select the user type");
lblSelectTheUser.setFont(new Font("Dialog", Font.BOLD, 15));
lblSelectTheUser.setBounds(22, 83, 192, 25);
frame.getContentPane().add(lblSelectTheUser);
JComboBox cb1 = new JComboBox();
cb1.setModel(new DefaultComboBoxModel(new String[] {"Student", "Lecturer", "Office staff", "HOD"}));
cb1.setBounds(213, 83, 151, 24);
frame.getContentPane().add(cb1);
}
public void setVisible(boolean b) {
// TODO Auto-generated method stub
}
public void setTitle(String string) {
// TODO Auto-generated method stub
}
public void setSize(int i, int j) {
// TODO Auto-generated method stub
}
public void setLocationRelativeTo(Object object) {
// TODO Auto-generated method stub
}
public void setDefaultCloseOperation(int exitOnClose) {
// TODO Auto-generated method stub
}
}

You can use
frame.setVisible(true);
to make a JFrame (form) visible.

AWT-EventQueue-0" StackOverflowError

Afternoon all, i have a problem with some JFrame code, this JFrame is started when the user presses "New User", and whenever they do so, i get:
Exception in thread "AWT-EventQueue-0" java.lang.StackOverflowError
at frontend.Registration.<init>(Registration.java:36)
at frontend.Registration.<init>(Registration.java:25)
at frontend.Registration.<init>(Registration.java:25)
at frontend.Registration.<init>(Registration.java:25)
With this code:
package frontend;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.SQLException;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.border.EmptyBorder;
public class Registration extends JFrame {
/**
*
*/
private static final long serialVersionUID = 1L;
private static boolean ranOnce = false;
private JPanel contentPane;
private Registration reg = new Registration();
private JTextField userTF;
private JTextField passTF;
private JTextField emailTF;
private LoginProcess lp = new LoginProcess();
private JLabel error;
/**
* Create the frame.
*/
public Registration() {
if (!ranOnce) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
ranOnce = true;
reg = new Registration();
reg.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 245, 195);
setLocationRelativeTo(null);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
setContentPane(contentPane);
contentPane.setLayout(null);
JLabel lblUsername = new JLabel("Username:");
lblUsername.setBounds(10, 11, 75, 14);
contentPane.add(lblUsername);
JLabel lblPassword = new JLabel("Password:");
lblPassword.setBounds(10, 36, 75, 14);
contentPane.add(lblPassword);
JLabel lblEmail = new JLabel("Email:");
lblEmail.setBounds(10, 61, 75, 14);
contentPane.add(lblEmail);
userTF = new JTextField();
userTF.setBounds(95, 8, 130, 20);
contentPane.add(userTF);
userTF.setColumns(10);
passTF = new JTextField();
passTF.setColumns(10);
passTF.setBounds(95, 33, 130, 20);
contentPane.add(passTF);
emailTF = new JTextField();
emailTF.setColumns(10);
emailTF.setBounds(95, 58, 130, 20);
contentPane.add(emailTF);
error = new JLabel("Error: Username already in use");
error.setBounds(10, 120, 215, 14);
contentPane.add(error);
JButton regBtn = new JButton("Register");
regBtn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
try {
if (lp.newUser(userTF.getText(), passTF.getText(), emailTF.getText())) {
reg.setVisible(false);
Main.mainFrame.setVisible(true);
} else {
if (lp.duplicateAccount) {
error.setText("lol");
}
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
regBtn.setBounds(10, 86, 215, 23);
contentPane.add(regBtn);
}
}
I know this error is caused by an infinite loop, or something. but i have a boolean in place to stop it from infinitely running. This code was working about 20mins ago, and i haven't changed the first part of the constructor since i created the code.
Any ideas? Thanks..

You create a new Object in the line private Registration reg = new Registration();.
You should create this object in the consturctor.

The problem at that line:
private Registration reg = new Registration();
You get in a infinite loop and then stack overflow.