Please paste ur code... It seems u are calling file chooser in constructor rather then in actionPerformed Method. Still itsnt clear until you paste your code.

Here is the code :

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package nysemarketpick;

import java.io.File;
import java.io.IOException;
import javax.swing.JFileChooser;

/**
 *
 * @author skiabox
 */
public class MainForm extends javax.swing.JFrame {

    /**
     * Creates new form MainForm
     */
    public MainForm() {
        initComponents();
    }

    /**
     * This method is called from within the constructor to initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is always
     * regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {

        fileChooser = new javax.swing.JFileChooser();
        mainPanel = new javax.swing.JPanel();
        jMenuBar1 = new javax.swing.JMenuBar();
        jMenu1 = new javax.swing.JMenu();
        Open = new javax.swing.JMenuItem();
        Exit = new javax.swing.JMenuItem();
        jMenu2 = new javax.swing.JMenu();
        jMenu3 = new javax.swing.JMenu();
        jMenu4 = new javax.swing.JMenu();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setTitle("Nyse Stock Pick");
        setSize(new java.awt.Dimension(1920, 1080));

        fileChooser.setDialogTitle("This is my open dialog");

        org.jdesktop.layout.GroupLayout mainPanelLayout = new org.jdesktop.layout.GroupLayout(mainPanel);
        mainPanel.setLayout(mainPanelLayout);
        mainPanelLayout.setHorizontalGroup(
            mainPanelLayout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(0, 1070, Short.MAX_VALUE)
        );
        mainPanelLayout.setVerticalGroup(
            mainPanelLayout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(0, 621, Short.MAX_VALUE)
        );

        jMenu1.setText("File");

        Open.setText("Open");
        Open.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                OpenActionPerformed(evt);
            }
        });
        jMenu1.add(Open);

        Exit.setText(" Exit");
        Exit.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                ExitActionPerformed(evt);
            }
        });
        jMenu1.add(Exit);

        jMenuBar1.add(jMenu1);

        jMenu2.setText("Options");
        jMenuBar1.add(jMenu2);

        jMenu3.setText("Tools");
        jMenuBar1.add(jMenu3);

        jMenu4.setText("Help");
        jMenuBar1.add(jMenu4);

        setJMenuBar(jMenuBar1);

        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(mainPanel, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
            .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                .add(layout.createSequentialGroup()
                    .add(0, 266, Short.MAX_VALUE)
                    .add(fileChooser, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                    .add(0, 266, Short.MAX_VALUE)))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(mainPanel, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(43, Short.MAX_VALUE))
            .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                .add(layout.createSequentialGroup()
                    .add(0, 135, Short.MAX_VALUE)
                    .add(fileChooser, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                    .add(0, 135, Short.MAX_VALUE)))
        );

        pack();
    }// </editor-fold>

    private void OpenActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        int returnVal = fileChooser.showOpenDialog(this);
        if (returnVal == JFileChooser.APPROVE_OPTION)
        {
            File file = fileChooser.getSelectedFile();
            //What to do with the file
            PriceVolumeChart chart = new PriceVolumeChart(file.getName());
            mainPanel = chart.myPanel;

        }
        else
        {
            System.out.println("File access cancelled by user.");
        }
    }

    private void ExitActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
        System.exit(0);
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        /*
         * Set the Nimbus look and feel
         */
        //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
        /*
         * If Nimbus (introduced in Java SE 6) is not available, stay with the
         * default look and feel. For details see
         * http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
         */
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(MainForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(MainForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(MainForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(MainForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        //</editor-fold>

        /*
         * Create and display the form
         */
        java.awt.EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                new MainForm().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify
    private javax.swing.JMenuItem Exit;
    private javax.swing.JMenuItem Open;
    private javax.swing.JFileChooser fileChooser;
    private javax.swing.JMenu jMenu1;
    private javax.swing.JMenu jMenu2;
    private javax.swing.JMenu jMenu3;
    private javax.swing.JMenu jMenu4;
    private javax.swing.JMenuBar jMenuBar1;
    private javax.swing.JPanel mainPanel;
    // End of variables declaration
}

Netbeans generates much of this code when you add a JFileChooser in a JFrame

I've fixed that by adding the fileChooser to Other Components node.

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