Develop Reference

Custom Swing "Tabbed Pane"

I'm trying to build a custom UI to practice my interface development.
What I would like to do is create a 'sidebar' on a JFrame, which acts as a tabbed pane for a number of JPanels that I would like to be able to switch between.
Currently, I have a 'sidebar' consisting of a number of buttons, and through clicking a button - I would 'hide' one panel, and 'swap in' another (although I am yet unsure of how best to do this). The panels I am creating are the same size, but I do not know how to swap a panel in one position on my UI with another panel, in that same position.
As a result of this I have researched tabbed panes, and these seem like they could be perfect for what I'm trying to implement. I know I can set each pane to display my own JPanel, but I would like the actual tabs to be represented by the custom buttons I have made.
Is this possible with the JTabbedPane class? Or should I continue figuring out how to swap in and out my panels using the button action listener?

JFrame with panel count depending from parameter

I am creating simple application in java - Eclipse - WindowBuilder Editor. JFrame`s contentPane has JGoodies FormLayout in which I have to place 3 or 4 Panels - depending on mode.
It is proper way to make if construction that decides if content pane will be divided 1x3 or 1x4(facilitation because between all I use relatedgaps and so on..)?
I am not sure if this is good approach but I do not know how can I do this in other way than if construction. It has to be practical and flexible approach - to handle resizing the window, et cetera..

Common approaches for dynamic layout include these:
Use revalidate(), and possibly repaint(), to layout a Container again after adding or removing components, as shown here.
Replace the layout and validate() the Container, as shown here.
Use CardLayout to replace one panel with another, as shown here and here.

Revamp Panel Based UI to JTabbed Panes

I have developed a simple music player in Java which can play any given playlist or simple mp3 song.
For now i have worked all things out in plain JPanels. GUI doesn't look neat.
I need to revamp the GUI using tabbed pane. How this can be achieved using existing JPanels without affecting current functionality?
Also, i am not able to figure out shall i go for Tabbed Pane or Card Layout?
http://docs.oracle.com/javase/tutorial/uiswing/layout/card.html
Because a tabbed pane provides its own GUI, using a tabbed pane is simpler than using the CardLayout class.

"Also, i am not able to figure out shall i go for Tabbed Pane or Card Layout?"
It really depends on your preference of the look of your program. The two layouts perform very similarly, though CardLayout is a little bit more code, though at all not difficult. If you don't want the tab look, which I don't see why you would, for a game, then go with CardLayout
"How this can be achieved using existing JPanels without affecting current functionality? "
You need to create separate JPanel for each containment of whatever components you want in each tab. Then just add those JPanel to the JTabbedPane. It shouldn't break any functionality, just the look. Components from another panel should not be affected, you just won't be able to see any changes made, unless that other panel is in view.
If you want to go with CardLayout you can look at the tutorial

Reusing a Dynamic JList with actionlisteners in CardLayout etc

I am creating a JList dynamically and I want to use it on different JPanels where I can call a setQuery(query); on it. There is a Search Button + field connected to it too. Is there a way to place the JList, search button and search field on like 10 different panels without having to duplicate the code everywhere? I can't place it on a seperate JPanel as it has other buttons / gui elements that need be around it depending on what JPanel is being displayed. I've looked everywhere but there is not much mention of reusing a dynamic JList.

You can place a component in one visualized container only. Consider creating a method that creates these components for you, that returns a JPanel that holds the components, and perhaps have all created JLists share the same ListModel, and all JButtons the same AbstractAction.
Or another option, if you are using CardLayout to swap JPanels, and you want all of the panels to hold these components above, consider not doing this but moving the JList, JButton, and JTextField out of the cards and on to a less dynamic portion of your GUI.
Also, this is not clear to me:
I can't place it on a seperate JPanel as it has other buttons / gui elements that need be around it depending on what JPanel is being displayed.
Please clarify and tell us more. Images might help as well.

Also consider the decorator pattern Your list/search panel would be the main component, while the variations would result from decorating the original.

Creating a GUI with multiple panels and one frame

I am trying to create a simple GUI. I have a menu bar that is filled with various JMenuItems. Each menu item should link to a different "window". Currently, I am thinking the best way to do this is to create a single frame, and create various JPanels. My ActionListeners will toggle visibility of the different panels, and only one panel should be visible at a time. Is this the best way to go about the task? Or is there a better workaround.

Yes, the best way is to use a CardLayout of which there's a great tutorial (please see the link), and many examples online including in this very forum, several of which I've written, including:
Java CardLayout Main Menu Problem
Change size of JPanel using CardLayout
Java CardLayout JPanel moves up, when second JPanel added
Java swing; How to toggle panel's visibility?
Clear components of JFrame and add new componets on the same JFrame
gui multiple frames switch
JLabel displaying countdown, java

JTabbedPane is already implemented for you!
JTabbedPane's tutorial.