Passing values between JFrames

First of all, your program design seems a bit off, as if you are using a JFrame for one of your windows where you should in fact be using a JDialog since it sounds as if one window should be dependent upon the other.

But regardless, you pass references of GUI objects the same as you would standard non-GUI Java code. If one window opens the other (the second often being the dialog), then the first window usually already holds a reference to the second window and can call methods off of it. The key often is when to have the first window call the second’s methods to get its state. If the second is a modal dialog, then the when is easy — immediately after the dialog returns which will be in the code immediately after you set the second dialog visible. If it is not a modal dialog, then you probably want to use a listener of some sort to know when to extract the information.

Having said this, the details will all depend on your program structure, and you’ll need to tell us more about this if you want more specific help.

For a simple example that has one window open another, allows the user to enter text into the dialog windows JTextField, and then places the text in the first window’s JTextField, please have a look at this:

import java.awt.Window;
import java.awt.Dialog.ModalityType;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.*;

public class WindowCommunication {

   private static void createAndShowUI() {
      JFrame frame = new JFrame("WindowCommunication");
      frame.getContentPane().add(new MyFramePanel());
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   // let's be sure to start Swing on the Swing event thread
   public static void main(String[] args) {
      java.awt.EventQueue.invokeLater(new Runnable() {
         public void run() {
            createAndShowUI();
         }
      });
   }
}

class MyFramePanel extends JPanel {
   private JTextField field = new JTextField(10);
   private JButton openDialogeBtn = new JButton("Open Dialog");

   // here my main gui has a reference to the JDialog and to the
   // MyDialogPanel which is displayed in the JDialog
   private MyDialogPanel dialogPanel = new MyDialogPanel();
   private JDialog dialog;

   public MyFramePanel() {
      openDialogeBtn.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            openTableAction();
         }
      });
      field.setEditable(false);
      field.setFocusable(false);

      add(field);
      add(openDialogeBtn);
   }

   private void openTableAction() {
      // lazy creation of the JDialog
      if (dialog == null) {
         Window win = SwingUtilities.getWindowAncestor(this);
         if (win != null) {
            dialog = new JDialog(win, "My Dialog",
                     ModalityType.APPLICATION_MODAL);
            dialog.getContentPane().add(dialogPanel);
            dialog.pack();
            dialog.setLocationRelativeTo(null);
         }
      }
      dialog.setVisible(true); // here the modal dialog takes over

      // this line starts *after* the modal dialog has been disposed
      // **** here's the key where I get the String from JTextField in the GUI held
      // by the JDialog and put it into this GUI's JTextField.
      field.setText(dialogPanel.getFieldText());
   }
}

class MyDialogPanel extends JPanel {
   private JTextField field = new JTextField(10);
   private JButton okButton = new JButton("OK");

   public MyDialogPanel() {
      okButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent e) {
            okButtonAction();
         }
      });
      add(field);
      add(okButton);
   }

   // to allow outside classes to get the text held by the JTextField
   public String getFieldText() {
      return field.getText();
   }

   // This button's action is simply to dispose of the JDialog.
   private void okButtonAction() {
      // win is here the JDialog that holds this JPanel, but it could be a JFrame or 
      // any other top-level container that is holding this JPanel
      Window win = SwingUtilities.getWindowAncestor(this);
      if (win != null) {
         win.dispose();
      }
   }
}

You’d do a very similar technique to get information out of a JTable.

And again, if this information doesn’t help you, then please tell us more about your program including showing us some of your code. The best code to show is a small compilable example, an SSCCE similar to what I’ve posted above.