Gridbag Layout and Tabbed Panes

Question

First off, I'm pretty new to Java, I started it around February as a school course, and it's been a pretty smooth ride. Recently, we started to code GUI, trying out different layouts and whatnot. I'm having a little trouble in this portion as our teacher did not really delve into it very much. My question concerns the GridBag layout within a panel of a tab (sorry if this is unclear, I'm talking about something that looks like this: http://www.codeproject.com/useritems/tabcontrol.asp). I don't know how to use GridBag constraints within a panel. What I used to do with GridBag was simply use some code that looked like (forgive me, this might not be very accurate): AddComponent button1(#, #, #, #) and define what each of those numbers meant later (first would be row, second would be column, third would be width, fourth would be height, for example). But now, with the tabs, each button, label, or any other control would be declared, then I would place a bunch of direct constraints after, like this:
JButton button1 = new JButton("1");
constraints.gridx = 0;
constraints.gridy = 0;
constraints.gridwidth = 1;
constraints.gridheight = 1;then add them into the panel like this:
panel1.add(button1, constraints);However, I have tried making the buttons on top of each other, and other patterns, but it would just place the buttons next to each other within the panel. How do I make it so that the constraints work? Or rather, if they do work, what kinda things might mess it up? I think the problem is that I dunno how to make the constraints specific to that one button.
Also, how do I make each panel a certain size instead of each panel being as small as possible to contain anything within it.
I'm sorry if this all sounds very vague, I'd be more than happy to give you any needed information. Also, I'm not asking any of you to do my homework, I just need a little clarification or an example. Just in case, here's the code I'm working on: http://hashasp.mine.nu/paster/?1376. Be aware that there are no comments or anything, it's very bare. Also, the form may be a bit messy because I'm pretty much reusing code that was given to me, just manipulating it in a different way. Thanks a lot in advanced for your time in reading this.

Answer 1

* GridBag_Demo.java
import java.awt.*;
import javax.swing.*;
public class GridBag_Demo extends JFrame {
    public GridBag_Demo() {
        setTitle("GridBag Demo");
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setSize(400,300);
        setLocationRelativeTo(null);
        GridBagConstraints gridBagConstraints;
        jTabbedPane1 = new JTabbedPane();
        jPanel1 = new JPanel();
        jButton1 = new JButton();
        jButton2 = new JButton();
        jButton3 = new JButton();
        jPanel1.setLayout(new GridBagLayout());
        jButton1.setText("jButton1");
        gridBagConstraints = new GridBagConstraints();
        gridBagConstraints.insets = new Insets(2,2,2,2);
        jPanel1.add(jButton1, gridBagConstraints);
        jButton2.setText("jButton2");
        gridBagConstraints.gridy = 1;
        jPanel1.add(jButton2, gridBagConstraints);
        jButton3.setText("jButton3");
        gridBagConstraints.gridy = 2;
        jPanel1.add(jButton3, gridBagConstraints);
        jTabbedPane1.addTab("tab1", jPanel1);
        getContentPane().add(jTabbedPane1, BorderLayout.CENTER);
    public static void main(String args[]) {
        new GridBag_Demo().setVisible(true);
    private JButton jButton1;
    private JButton jButton2;
    private JButton jButton3;
    private JPanel jPanel1;
    private JTabbedPane jTabbedPane1;
}