Java.lang.stackoverflowerror issue when calling another jframe

Question

i created a login screen with a username/password field that i call from my main applicaton. I call the jframe with the following code
  createDirectories();
        startNotes();
        login.start();
        getLists();once it gets to the login.start(); it give the following error
Exception in thread "AWT-EventQueue-0" java.lang.StackOverflowError
at sun.awt.Win32GraphicsConfig.getBounds(Native Method)
at sun.awt.Win32GraphicsConfig.getBounds(Win32GraphicsConfig.java:240)
at java.awt.Window.init(Window.java:368)
at java.awt.Window.<init>(Window.java:407)
here is the full code for my login.java minus the swing component creation
import javax.swing.JOptionPane;
public class loginScreen extends javax.swing.JFrame {
    TESTapplication app = new TESTapplication();
        patientObject patient = new patientObject();
    public loginScreen() {       
        initComponents();        
   //initcomponents removed from here
private void btnLoginActionPerformed(java.awt.event.ActionEvent evt) {                                        
        sendLogin();
    private void btnCancelActionPerformed(java.awt.event.ActionEvent evt) {                                         
        System.out.println("User exited application");
        System.exit(3);
     * @param args the command line arguments
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {              
             // start();
    // Variables declaration - do not modify                    
    private javax.swing.JButton btnCancel;
    private javax.swing.JButton btnLogin;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel lblLoginInfo;
    private javax.swing.JPasswordField pswrdFldPassword;
    private javax.swing.JTextField txtFldUsername;
    // End of variables declaration                  
    public void start(){
        new loginScreen().setVisible(true);
    public void sendLogin(){
        if (
                txtFldUsername.getText().trim().equals("") ||  //trim removes whitespace
                pswrdFldPassword.getText().trim().equals("") )
            JOptionPane.showMessageDialog(null,"Complete empty field(s)","Warning",JOptionPane.WARNING_MESSAGE);
        } else {
            patient.setUsername(txtFldUsername.getText().trim());
            patient.setPassword(pswrdFldPassword.getText().trim());
            patient.setAction("login");
            app.sendPatient();
}thanks for all help given

Answer 1

I only need to call 1 new login screen and no new application... how can i call a
function from another java file?From a method of any class you can invoke (call) methods of other classes. I use "method" rather than "function" here to emphasise that they are much more than bits of code that do something: they have a context (the object of which they are a method).
for instance i want to call the start function of the loginScreen.java from the
testapplication.java. i don't need any new pieces, just want to be able to open the
loginscreen jframe from the test application jframe.I wondered before why that start() method was creating a new loginScreen, but leaving that aside... One way might be for the TESTapplication class to have a member variable of type loginScreen. When some method of TESTapplication wants to invoke the start() method it just does so:loginScreen myLoginScreen = new loginScreen();
// much later...
myLoginScreen.start();There is no need for the loginScreen to have its own TESTapplication member variable since, as you say. "i don't need any new pieces".
The start() method appears to next to nothing. It makes the loginScreen instance visible. But there's already a public method to do that. Perhaps loginScreen should be a modal JDialog: calling setVisible(true) will allow the login screen to do its thing and not return until it has finished (without blocking the event queue).
It's all really a bit speculative and will remain so until you break down your application into small pieces: not functions (actions), but classes (types of obejcts including the things they can do.) Each class should have a clear and documented description of what it does.