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Center Panel's Component Within a java swing BoxLayout

I'm trying to use a BoxLayout to display 2 panels vertically and I searched how to center the components in those panels. At the moment, my components are placed on the top center of each panel, and I want to get them at the center X and Y.
I added the components I want in the 2 panels, then I added the panels in my BoxLayout. This way they're displayed vertically as I want them to be, but as I said I don't want them to be on top center.
I tried to use methods such as setAlignementY and setLocation but any of them actually moves the components. I also saw that a BoxLayout will try to set the components as wide as the widest component, but as I have only 2 panels which have the same size I don't really understand it.
This is basically how I've added my components (without trying to center) :
private void initPanels ()
{
this.titlePanel.add(this.title);
this.bookInputPanel.add(bookTitle);
this.bookInputPanel.add(bookInput);
this.authorInputPanel.add(by);
this.authorInputPanel.add(authorInput);
this.authorInputPanel.add(this.authorsTable);
this.buttonsPanel.add(confirm);
this.contentPanel.setLayout(new BoxLayout(this.contentPanel, BoxLayout.Y_AXIS));
this.contentPanel.add(bookInputPanel);
this.contentPanel.add(authorInputPanel);
this.add(this.titlePanel, BorderLayout.NORTH);
this.add(this.contentPanel, BorderLayout.CENTER);
this.add(this.buttonsPanel, BorderLayout.SOUTH);
}
I made a picture to show you exactly what I want but it seems that I need 10 rep to do it, sorry about that.

This way they're displayed vertically as I want them to be, but as I said I don't want them to be on top center.
One way is to add "glue" to the top/bottom of the panel. This "glue" will expand to fill the extra space available to the panel:
this.contentPane.add(Box.createVerticalGlue());
this.contentPanel.add(bookInputPanel);
this.contentPanel.add(authorInputPanel);
this.contentPane.add(Box.createVerticalGlue());
Read the section from the Swing tutorial on How to Use BoxLayout for more information about the feature of a BoxLayout.
Another option might be to use a "wrapper" panel that uses a different layout manager. For example the GridBagLayout with the default constraints will automatically center the component horizontally/vertically:
//this.add(this.contentPanel, BorderLayout.CENTER);
JPanel wrapper = new JPanel( new GridBagLayout() );
wrapper.add( contentPanel );
this.add(wrapper, BorderLayout.CENTER);

JScrollPane does not update scrollbar

I am trying to create a JScrollPane that contains a JPanel that will be increasing and decreasing in height. When it becomes larger than the size of the JScrollPane, it should create a vertical scroll bar which will allow me to scroll through the entire JPanel. However, I am having difficulty achieving this. Yes, I know I am not using LayoutManagers. No, I will not be using them, and I need a solution that does not involve their usage.
Here are the two button's AbstractActions that add and subtract from the JPanel:
class AddACT extends AbstractAction
{
public void actionPerformed(ActionEvent e)
{
info.setSize(420,info.getHeight() + 40);
info.add(new SubPanel); // Adds another JPanel into the main JPanel (for content input)
gui.repaint();
infoS.validate();
}
}
class RemoveACT extends AbstractAction
{
public void actionPerformed(ActionEvent e)
{
info.remove(subPanel()); // This would remove the last JPanel added to the main JPanel
info.setSize(420,info.getHeight() - 40);
gui.repaint();
infoS.validate();
}
And here is the code for the main JPanel and the JScrollPane:
final JPanel info = new JPanel();
final JScrollPane infoS = new JScrollPane(info, ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
info.setLayout(null);
info.setSize(420,600);
infoS.setLocation(10,80);
infoS.setSize(420,490);
gui.add(infoS); // gui is the frame's content pane (the overall JPanel)
This is the second project I've been trying to learn GUI by doing. I am a complete novice in Swing and am only intermediate in Java. Sorry if I am making a blindingly obvious mistake.

1) Use LayoutManagers (+1 to #kleopatra and #GagandeepBali comments)
The absence of LayoutManagers only guarantees your GUI's will look very trashy (especially when run on other OSes/builds) and being a Novice you should rather learn the correct way than learn the wrong way and get into bad habits like calling setSize() etc.
Have a read on these links to get you started:
A Visual Guide to Layout Managers
Concurrency in Swing
2) See this example for how to use a JScrollPane, it simply adds a JPanel with buttons to a JScrollPane which in-turn is added to the JFrame.
3) Also see this example for how to make the JScrollPane vertically scroll-able only.
4) For more on JScrollPanes have a look here: How to Use Scroll Panes.
5) As for how it interacts with LayoutManager, if you do not explicitly set its size via setPreferredSize(Dimension d) the scroll pane computes it based on the preferred size of its nine components (the viewport, and, if present, the two scroll bars, the row and column headers, and the four corners)
6) On your usage of validate():
validate() is used when new JComponents are added to a visible component
revalidate() is used when JComponent is removed/added from a visible component
revalidate() covers validate() too
Thus always use this:
//add or remove component(s)
revalidate();
repaint();
References:
http://www.daniweb.com/software-development/java/threads/405568/validate-vs-revalidate

LayoutManager is not required to solve the problem. The problem in Thrfoot's example is in these lines:
final JScrollPane infoS = new JScrollPane(info, ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
info.setLayout(null);
info.setSize(420,600);
The program appears to recognize there is a need for scroll bars (it would show the scroll bar if your setting was VERTICAL_SCROLLBAR_AS_NEEDED), but the actual scrolling does not work (the scroll bar slider is not there).
To fix this, first set the preferred size of info, then construct the infoS.
Example:
info.setPreferredSize(420,600);
final JScrollPane infoS = new JScrollPane(info, ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
The idea is to set the preferred size of the info panel before it is used for the scroll pane. This is the same reason to set the size and location of infoS before adding to the gui:
infoS.setLocation(10,80);
infoS.setSize(420,490);
gui.add(infoS); // gui is the frame's content pane (the overall JPanel)

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!

How do I make JScrollPane work properly with nested JPanels?

I'm building a Swing application in Java using NetBeans and I have a problem with layout. My main frame contains a JScrollPane which contains a JPanel called contentPanel which in turn contains a JPanel called listPanel. The listPanel is empty when the program starts, but when the user interacts with the program an unpredictable number of smaller JPanels are added to it. I've used the NetBeans GUI-builder to snap the top edge of listPanel to the top of contentPanel, and the same with the bottom edges.
The problem I have is that when more components are added to listPanel the vertical scrollbar doesen't appear on my scrollpane. The verticalScrollBarPolicy of my scrollpane is set to AS_NEEDED and its viewportView is set to contentPanel. What I think I need to do is to make contentPanel grow when more items are added to listPanel.

The problem I have is that when more components are added to listPanel the vertical scrollbar doesen't appear on my scrollpane.
The scrollbar will appear when the preferred size of the component added to the scrollpane is greater than the size of the scrollpane. When you add components dynamically you need to tell the scrollpane something has changed. So you basic code should be:
panel.add( subPanel );
panel.revalidate();
Or, because you are adding a panel to the sub panel, you may need to revalidate the scrollpane (I don't remember):
panel.add( subPanel );
scrollPane.revalidate();
The key is the revalidate() which tell the layout manager to recalculate its size.

Use a different LayoutManager. One that will allow for vertical growth like BoxLayout. Also remember that you can use multiple layouts and nest them inside of each other for different effects.

How to make JLabels start on the next line

JPanel pMeasure = new JPanel();
....
JLabel economy = new JLabel("Economy");
JLabel regularity = new JLabel("Regularity");
pMeasure.add(economy);
pMeasure.add(regularity);
...
When I run the code above I get this output:
Economy Regularity
How can I get this output, where each JLabel starts on a new line? Thanks
Economy
Regularity

You'll want to play around with layout managers to control the positioning and sizing of the controls in your JPanel. Layout managers are responsible for placing controls, determining where they go, how big they are, how much space is between them, what happens when you resize the window, etc.
There are oodles of different layout managers each of which allows you to layout controls in different ways. The default layout manager is FlowLayout, which as you've seen simply places components next to each other left to right. That's the simplest. Some other common layout managers are:
GridLayout - arranges components in a rectangular grid with equal-size rows and columns
BorderLayout - has one main component in the center and up to four surrounding components above, below, to the left, and to the right.
GridBagLayout - the Big Bertha of all the built-in layout managers, it is the most flexible but also the most complicated to use.
You could, for example, use a BoxLayout to layout the labels.
BoxLayout either stacks its components on top of each other or places them in a row — your choice. You might think of it as a version of FlowLayout, but with greater functionality. Here is a picture of an application that demonstrates using BoxLayout to display a centered column of components:
An example of code using BoxLayout would be:
JPanel pMeasure = new JPanel();
....
JLabel economy = new JLabel("Economy");
JLabel regularity = new JLabel("Regularity");
pMeasure.setLayout(new BoxLayout(pMeasure, BoxLayout.Y_AXIS));
pMeasure.add(economy);
pMeasure.add(regularity);
...

I read this piece of code:
pMeasure.setLayout(new BoxLayout(pMeasure, BoxLayout.VERTICAL));
It seems BoxLayout doesn't have VERTICAL. Upon searching, this will work using the following code:
pMeasure.setLayout(new BoxLayout(pMeasure, BoxLayout.Y_AXIS));

Here is what you need to use:
JLabel economy = new JLabel("<html>Economy<br>Regularity</html>");

A quick way is to use html within the JLabel.
For instance include the <br/> tag.
Otherwise, implement a BoxLayout.

Make a separate JPanel for each line, and set the dimensions to fit each word:
JLabel wordlabel = new JLabel("Word");
JPanel word1 = new JPanel();
word1.setPreferredSize(new Dimension(#,#);
This should work for each word. You can then add each of those JPanels to your main JPanel. This also allows you to add other components next to each word.