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Java add more than one JPanel objects into JFrame

I am a beginer and I dont know how to add more objects into JFrame.
How could I add more than one JPanel objects into JFrame?
Below is what I have tried.
Thanks for your help.
public class Init extends JFrame{
public Init(){
super("Ball");
Buttons t = new Buttons();
JumpingBall b1 = new JumpingBall();
JumpingBall b2 = new JumpingBall();
t.addBall(b1);
t.addBall(b2);
add(b1);
add(b2);
setSize(500,500);
setResizable(false);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setLocationRelativeTo(null);
}
}

Assuming that JumpingBall extends JPanel, you might want to have a look at the java layout managers here: Link.
The default Layout for a JFrame is the BorderLayout and if you didn't specify where you want to add your component, The BorderLayout will put it in the center by default. In BorderLayout, you cannot have more that one component in the same area. So, in your example you will end up having only the second JumpingBall panel in your frame. If you want to have more than one component at the center, then you will have to create a JPanel and add those components to it using different Layout. The common three Layouts are the BorderLayout, FlowLayout and GridLayout Please have a look at the provided link above to see how the components are arranged.

You can add a number of JPanel objects in a JFrame, using the add method. If only one is displayed, you might need to change your Layout options or use a Layout Manager (Look here for more).

You are seeing only one because it overlapping each other. Just provide setbound(x,y,x1,y1) for you panel component and you will see your panel at location.
or use setLayout(new FlowLayout()); which is going to order your component in respective to other so you will not override each-other.

How can I position a JButton under a JTable?

How can I position a JButton under a JTable? What kind of layouts? How? I have a JTable table what is scrollable, and the table is in a frame.

There are many layouts to fulfill this need.
The simplest is using BorderLayout:
JFrame frame = new JFrame();
Container contentPane = frame.getContentPane();
contentPane.setLayout(new BorderLayout());
contentPane.add(new JScrollPane(jtable), BorderLayout.CENTER);
contentPane.add(button, BorderLayout.SOUTH);
If you want this button to be not resized just add JPanel to contentPane. This JPanel should contain your button centered using almost any layout.
If you would like to use more sophisticated layout - the best in my opinion is MigLayout

To correct LoveToCode's well-meaning but misleading advice, you would never want to give a JTable itself a layout. The solution to your problem is not to set the JTable's layout but to set the layout for the JPanel that holds both the JTable's JScrollPane and the JButton. Likely a BorderLayout would work best with the JScrollPane being placed BorderLayout.CENTER and the JPanel that holds the JButton BorderLayout.SOUTH.
Note, if you're adding these components to the JFrame, then know that its contentPane already uses BorderLayout (the tutorials will tell you this -- please read them). So just add these guys to the contentPane as described above.

If hard coding of swing and awt is not mandatory, try using the WindowsBuilder Pro, a Free tool now from google, install its plugin in to eclipse, then Use
GroupLayout - Introduced by NetBeans team in 2005 integrated in WindowsBuilder Pro, is one of the most convenient way create a good gui in less time in Java.

It seems that you can set the layout of a jtable the same way in which you can set the layout of a jframe or a jpane:
table.setLayout(new grideLayout(4, 3)
would give it a grid layout with 4 rows and 3 columns.
the scrollable feature allows you to 'scroll' through your table with the moving bar. It may be a default feature, or it may be that you must use it, try seeing what methods your table gives you.
Lastly, your table should be in a frame, so that you can view it on your window, make you class extend JFrame and it will automatically be a frame upon which you can simply add a table!

auto resize JTabbedPane

Is there any way to autoresize a JTabbedPane to the same size that the JFrame has?
I'm using netbeans to create the swing interface and I can't figure out whether this is a property that I can set through the GUI designer or if I have to do it programmatically. If I need to do it programatically, netbeans doesn't allow users to modify the auto generated UI code.
Thanks a lot in advance

The Visual Guide to Layout Managers should be useful for understanding how components are arranged in container.
For your task I would use BorderLayout and placed the JTabbedPane into it's center area.
For example:
frame.getContentPane().setLayout(new BorderLayout());
frame.getContentPane().add(pane, BorderLayout.CENTER);
In netbeans you just change your frame layout to BorderLayout and after that in properties for the JTabbedPane set layout constraint CENTER

Java netbeans autoresize textarea

I am using netbeans 7.0.1 to build a simple JFrame application
I am putting a textarea and a couple of buttons on using the gui builder
the buttons are on the same vertical level and the right hand button shifts right on resize of the window - that is fine but I would like the text area to do the same - i.e. resize to fit the relevant width of the window.
For the life of me I cannot see how this is done - I have looked around and I can find code for a hand coded app but not for netbeans gui builder

Update: Ah sorry, didn't read the full question, you really want to do it with netbeans.. :) Well, well, now you have this post how to do it hand-crafted aswell! :)
I wouldn't use an GUI builder for this task. It is easy to create such layout with FlowLayout and BorderLayout:
Screenshot was produced by this code:
public static void main(String... args) throws Exception {
JFrame frame = new JFrame("Test");
JPanel buttonPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT));
buttonPanel.add(new JButton("Hello"));
buttonPanel.add(new JButton("World!"));
frame.add(buttonPanel, BorderLayout.NORTH);
frame.add(new JTextArea("Hello World!"), BorderLayout.CENTER);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(600, 400);
frame.setVisible(true);
}

It's all about the layout you're using. I would personally use GridBagLayout, probably because I am accustomed to it. Basically, you should follow these steps:
Change the layout of the container which owns the textarea to GridBagLayout. You can do that by right-clicking on the container(being it the JFrame, a panel, whatever) and there you will see the Layout menu. It contains a GridBagLayout option.
In the component inspector select the JScrollPane that owns the JTextArea. Check out the "Layout" section in the properties tab. It contains the GridBagConstraints which command the layout behaviour of the JScrollPane and thus commands the JTextArea.
Play with the layout properties :). Basically you should set the X and Y weight to 1, and the Fill to "Both". This will tell the JScrollPane to fill any vertical and horizontal space there is on the Frame, and the X and Y weight will pull any other components as far as possible.
You can read more about GridBagLayout here: http://netbeans.org/kb/docs/java/gbcustomizer-basic.html
Learning GridBagLayout could take a couple of hours, getting used to it could take a couple of days, but it's worth learning. Just my 2 cents.

adding multiple jPanels to jFrame

I want to add two jPanels to a JFrame side by side. the two boxes are jpanels and the outer box is a jframe
I have these lines of code. I have one class called seatinPanel that extends JPanel and inside this class I have a constructor and one method called utilityButtons that return a JPanel object. I want the utilityButtons JPanel to be on the right side. the code I have here only displays the utillityButtons JPanel when it runs.
public guiCreator()
{
setTitle("Passenger Seats");
//setSize(500, 600);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
Container contentPane = getContentPane();
seatingPanel seatingPanel1 = new seatingPanel();//need to declare it here separately so we can add the utilityButtons
contentPane.add(seatingPanel1); //adding the seats
contentPane.add(seatingPanel1.utilityButtons());//adding the utility buttons
pack();//Causes this Window to be sized to fit the preferred size and layouts of its subcomponents
setVisible(true);
}

The most flexible LayoutManager I would recommend is BoxLayout.
You can do the following :
JPanel container = new JPanel();
container.setLayout(new BoxLayout(container, BoxLayout.X_AXIS));
JPanel panel1 = new JPanel();
JPanel panel2 = new JPanel();
//panel1.set[Preferred/Maximum/Minimum]Size()
container.add(panel1);
container.add(panel2);
then add container to object to your frame component.

You need to read up on and learn about the layout managers that Swing has to offer. In your situation it will help to know that a JFrame's contentPane uses BorderLayout by default and you can add your larger center JPanel BorderLayout.CENTER and the other JPanel BorderLayout.EAST. More can be found here: Laying out Components in a Container
Edit 1
Andrew Thompson has already shown you a bit on layout managers in his code in your previous post here: why are my buttons not showing up?. Again, please read the tutorial to understand them better.