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What is the functional difference between creating a Java frame inside the main class and creating a Java Frame inside a constructor? [duplicate]

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I'm developing an application which displays images, and plays sounds from a database. I'm trying to decide whether or not to use a separate JFrame to add images to the database from the GUI.
I'm just wondering whether it is good practice to use multiple JFrame windows?

I'm just wondering whether it is good practice to use multiple JFrames?
Bad (bad, bad) practice.
User unfriendly: The user sees multiple icons in their task bar when expecting to see only one. Plus the side effects of the coding problems..
A nightmare to code and maintain:
A modal dialog offers the easy opportunity to focus attention on the content of that dialog - choose/fix/cancel this, then proceed. Multiple frames do not.
A dialog (or floating tool-bar) with a parent will come to front when the parent is clicked on - you'd have to implement that in frames if that was the desired behavior.
There are any number of ways of displaying many elements in one GUI, e.g.:
CardLayout (short demo.). Good for:
Showing wizard like dialogs.
Displaying list, tree etc. selections for items that have an associated component.
Flipping between no component and visible component.
JInternalFrame/JDesktopPane typically used for an MDI.
JTabbedPane for groups of components.
JSplitPane A way to display two components of which the importance between one or the other (the size) varies according to what the user is doing.
JLayeredPane far many well ..layered components.
JToolBar typically contains groups of actions or controls. Can be dragged around the GUI, or off it entirely according to user need. As mentioned above, will minimize/restore according to the parent doing so.
As items in a JList (simple example below).
As nodes in a JTree.
Nested layouts.
But if those strategies do not work for a particular use-case, try the following. Establish a single main JFrame, then have JDialog or JOptionPane instances appear for the rest of the free-floating elements, using the frame as the parent for the dialogs.
Many images
In this case where the multiple elements are images, it would be better to use either of the following instead:
A single JLabel (centered in a scroll pane) to display whichever image the user is interested in at that moment. As seen in ImageViewer.
A single row JList. As seen in this answer. The 'single row' part of that only works if they are all the same dimensions. Alternately, if you are prepared to scale the images on the fly, and they are all the same aspect ratio (e.g. 4:3 or 16:9).

The multiple JFrame approach has been something I've implemented since I began programming Swing apps. For the most part, I did it in the beginning because I didn't know any better. However, as I matured in my experience and knowledge as a developer and as began to read and absorb the opinions of so many more experienced Java devs online, I made an attempt to shift away from the multiple JFrame approach (both in current projects and future projects) only to be met with... get this... resistance from my clients! As I began implementing modal dialogs to control "child" windows and JInternalFrames for separate components, my clients began to complain! I was quite surprised, as I was doing what I thought was best-practice! But, as they say, "A happy wife is a happy life." Same goes for your clients. Of course, I am a contractor so my end-users have direct access to me, the developer, which is obviously not a common scenario.
So, I'm going to explain the benefits of the multiple JFrame approach, as well as myth-bust some of the cons that others have presented.
Ultimate flexibility in layout - By allowing separate JFrames, you give your end-user the ability to spread out and control what's on his/her screen. The concept feels "open" and non-constricting. You lose this when you go towards one big JFrame and a bunch of JInternalFrames.
Works well for very modularized applications - In my case, most of my applications have 3 - 5 big "modules" that really have nothing to do with each other whatsoever. For instance, one module might be a sales dashboard and one might be an accounting dashboard. They don't talk to each other or anything. However, the executive might want to open both and them being separate frames on the taskbar makes his life easier.
Makes it easy for end-users to reference outside material - Once, I had this situation: My app had a "data viewer," from which you could click "Add New" and it would open a data entry screen. Initially, both were JFrames. However, I wanted the data entry screen to be a JDialog whose parent was the data viewer. I made the change, and immediately I received a call from an end-user who relied heavily on the fact that he could minimize or close the viewer and keep the editor open while he referenced another part of the program (or a website, I don't remember). He's not on a multi-monitor, so he needed the entry dialog to be first and something else to be second, with the data viewer completely hidden. This was impossible with a JDialog and certainly would've been impossible with a JInternalFrame as well. I begrudgingly changed it back to being separate JFrames for his sanity, but it taught me an important lesson.
Myth: Hard to code - This is not true in my experience. I don't see why it would be any easier to create a JInternalFrame than a JFrame. In fact, in my experience, JInternalFrames offer much less flexibility. I have developed a systematic way of handling the opening & closing of JFrames in my apps that really works well. I control the frame almost completely from within the frame's code itself; the creation of the new frame, SwingWorkers that control the retrieval of data on background threads and the GUI code on EDT, restoring/bringing to front the frame if the user tries to open it twice, etc. All you need to open my JFrames is call a public static method open() and the open method, combined with a windowClosing() event handles the rest (is the frame already open? is it not open, but loading? etc.) I made this approach a template so it's not difficult to implement for each frame.
Myth/Unproven: Resource Heavy - I'd like to see some facts behind this speculative statement. Although, perhaps, you could say a JFrame needs more space than a JInternalFrame, even if you open up 100 JFrames, how many more resources would you really be consuming? If your concern is memory leaks because of resources: calling dispose() frees all resources used by the frame for garbage collection (and, again I say, a JInternalFrame should invoke exactly the same concern).
I've written a lot and I feel like I could write more. Anyways, I hope I don't get down-voted simply because it's an unpopular opinion. The question is clearly a valuable one and I hope I've provided a valuable answer, even if it isn't the common opinion.
A great example of multiple frames/single document per frame (SDI) vs single frame/multiple documents per frame (MDI) is Microsoft Excel. Some of MDI benefits:
it is possible to have a few windows in non rectangular shape - so they don't hide desktop or other window from another process (e.g. web browser)
it is possible to open a window from another process over one Excel window while writing in second Excel window - with MDI, trying to write in one of internal windows will give focus to the entire Excel window, hence hiding window from another process
it is possible to have different documents on different screens, which is especially useful when screens do not have the same resolution
SDI (Single-Document Interface, i.e., every window can only have a single document):
MDI (Multiple-Document Interface, i.e., every window can have multiple documents):

I'd like to counter the "not user friendly" argument with an example that I have just been involved with.
In our application we have a main window where the users run various 'programs' as separate tabs. As much as possible we have tried to keep our application to this single window.
One of the 'programs' they run presents a list of reports that have been generated by the system, and the user can click on an icon on each line to pop open a report viewer dialog. This viewer is showing the equivalent of the portrait/landscape A4 page(s) of the report, so the users like this window to be quite big, almost filling their screens.
A few months ago we started getting requests from our customers to make these report viewer windows modeless, so that they could have multiple reports open at the same time.
For some time I resisted this request as I did not think this was a good solution. However, my mind was changed when I found out how the users were getting around this 'deficiency' of our system.
They were opening a viewer, using the 'Save As' facility to save the report as a PDF to a specific directory, using Acrobat Reader to open the PDF file, and then they would do the same with the next report. They would have multiple Acrobat Readers running with the various report outputs that they wanted to look at.
So I relented and made the viewer modeless. This means that each viewer has a task-bar icon.
When the latest version was released to them last week, the overwhelming response from them is that they LOVE it. It's been one of our most popular recent enhancements to the system.
So you go ahead and tell your users that what they want is bad, but ultimately it won't do you any favours.
SOME NOTES:
It seems to be best practice to use JDialog's for these modeless windows
Use the constructors that use the new ModalityType rather than the boolean modal argument. This is what gives these dialogs the task-bar icon.
For modeless dialogs, pass a null parent to the constructor, but locate them relative to their 'parent' window.
Version 6 of Java on Windows has a bug which means that your main window can become 'always on top' without you telling it. Upgrade to version 7 to fix this

Make an jInternalFrame into main frame and make it invisible. Then you can use it for further events.
jInternalFrame.setSize(300,150);
jInternalFrame.setVisible(true);

It's been a while since the last time i touch swing but in general is a bad practice to do this. Some of the main disadvantages that comes to mind:
It's more expensive: you will have to allocate way more resources to draw a JFrame that other kind of window container, such as Dialog or JInternalFrame.
Not user friendly: It is not easy to navigate into a bunch of JFrame stuck together, it will look like your application is a set of applications inconsistent and poorly design.
It's easy to use JInternalFrame This is kind of retorical, now it's way easier and other people smarter ( or with more spare time) than us have already think through the Desktop and JInternalFrame pattern, so I would recommend to use it.

Bad practice definitely. One reason is that it is not very 'user-friendly' for the fact that every JFrame shows a new taskbar icon. Controlling multiple JFrames will have you ripping your hair out.
Personally, I would use ONE JFrame for your kind of application. Methods of displaying multiple things is up to you, there are many. Canvases, JInternalFrame, CardLayout, even JPanels possibly.
Multiple JFrame objects = Pain, trouble, and problems.

I think using multiple Jframes is not a good idea.
Instead we can use JPanels more than one or more JPanel in the same JFrame.
Also we can switch between this JPanels. So it gives us freedom to display more than on thing in the JFrame.
For each JPanel we can design different things and all this JPanel can be displayed on the single JFrameone at a time.
To switch between this JPanels use JMenuBar with JMenuItems for each JPanelor 'JButtonfor eachJPanel`.
More than one JFrame is not a good practice, but there is nothing wrong if we want more than one JFrame.
But its better to change one JFrame for our different needs rather than having multiple JFrames.

If the frames are going to be the same size, why not create the frame and pass the frame then as a reference to it instead.
When you have passed the frame you can then decide how to populate it. It would be like having a method for calculating the average of a set of figures. Would you create the method over and over again?

It is not a good practice but even though you wish to use it you can use the singleton pattern as its good. I have used the singleton patterns in most of my project its good.

Java graphic as an object/class

I'm sorry this is probably way too basic to be on here, but it's a subject I've been struggling with for about a month now and I don't know where else to go (as far as I know there is no "noob overflow", lol).
I'm trying to create a class that would:
1. put an image on a window (a JFrame, JPanel or other container)
2. be able to support keyboard and mouse listeners
3. could have multiple instances in the same container
So anyway I've tried all the usual places - Google, YouTube, the official Java site (sorry forgot the URL) and of course here on Stack Overflow - but haven't been able to find anything even remotely similar to what I'm trying to do.
Of course, I've also considered the possiblity that maybe it can't be done at all. There doesn't seem to be any kind of standard "JImage" or "JGraphic" that works like JButton or JLabel, and for whatever reason graphics requires a completely different list of (extremely involved) processes and procedures. As an example, in this post: How to "really" draw images in a Java app - it took me 60+ lines of code and 2 classes to just come close. That project didn't work in the end because for some reason it would only let me create one instance (even it you created 2-4 in the main method, it would only display the last one you told it to add).
But anyway, assuming that I'm not trying to "re-invent the wheel" here and it is actually possible (in Java), does anyone have an idea as to how (or at least know of a better site to study it)? Unfortunately most of the sites I've visited tend to assume you know all the inner workings of images (I know what a pixel is but that's about it - Buffers, Rastars etc. are still beyond me). It would be absolutely outstanding if there were a site that would explain it in layman's terms, if such a site exists. Thanks in advance.

Just use a plain old JLabel.
Regarding your requirements:
put an image on a window (a JFrame, JPanel or other container).
You can give a JLabel an ImageIcon of the image of interest and it will display it. This can then be easily placed in any other container such as a JPanel or JFrame.
be able to support keyboard and mouse listeners
Any component that extends JComponent, such as a JLabel allows for use of MouseListener, MouseMotionListener and can listen for keyboard input via Key Bindings.
could have multiple instances in the same container
You can add as many as you'd like to any container. Just be cognizant and respectful of the layout managers in use.

Java Swing: flyweight vs new windows

I'm developing a new application where I'll have some windows opened at the same time.
I'm currently trying to design the GUI and I'm struggling with two choices:
I could use a side navigation panel and using the center of the page to display the content of each panel. These panels would be stored according flyweight pattern and I would just hide/show them when navigation buttons are clicked (in order to save the content as is was when hidden, for example a user registration form).
I could use a front page displaying the menu all over it and use popups/new windows to show the content. These could be closed/minimized etc).
My problem is: What if all the panels are stored in my flyweight pattern? will it have a huge performance hit or will it still run smoothly with like 15 JPanels stored? (of course those JPanels will have sometimes lots of content in it such as forms etc).
What do you think would be the best easy-to-use/performance choice ?
Thank you :)

JTable rendering already uses the flyweight pattern, so a one column table is ideal for selection. A custom renderer can display an arbitrary thumbnail representation, while a ListSelectionListener can display arbitrary detail in an adjacent container. In the TableModel, consider an LRU cache if the individual data records are consuming too much memory.
As always with performance questions, prototype and profile.

As long as you don't attempt to hold more data than fits the heap reasonably, performance will be a non-issue nowadays (unless you do something exceptionally bad you will not notice any performance difference from the user perspective).
That said, unless you have pressing reason to hold on to GUI's you currently don't need - just let them get GC'd and recreate them as needed. The create-throw-away after one use approach is more flexible when the application needs to be modified and bears less opportunities for memory leaks.
As for the GUI design aspect, many people absolutely hate popups. They can also interfere with focus management/keyboard usage. But it still depends on which kind of control flow you need. Side menu bar is fine for many purposes.
I'd like to point out that the side menu is just a fancy reinvention of Tabbed Pane (which is a standard component you wouldn't need to implement yourself). Also, if things need to be done in a specific order - a Wizard like approach can also be a good choice (one Window that changes contents with each step completed).

Swing GUI - Creating a 'Settings' Window (Properly)

I am working on an application that uses Swing. I have successfully created a main GUI for the user to work from. However, I would like to allow the user to change his/her settings. How should I go about creating the settings window? Would using a new JFrame called 'Settings' be the best way to handle this, or is there something better to use than a second JFrame?
(Note: The settings JFrame, on exit, will not close the main GUI, it will use the DISPOSE method)
I would like to handle this in a way that consumes the least amount of memory, but maintaining a professionalized look to the application.

Have you considered a CardLayout? http://docs.oracle.com/javase/tutorial/uiswing/layout/card.html
Personally, I find the use of a separate dialogue to be a bit dated for configuration settings. I prefer tabbed layouts, which are card layouts decorated with a tab bar across the top.
You could easily wrap your application in a near-top-level card layout and add a menu action to switch to the configuration card, with the "acknowledgement" or "cancel" buttons switching back to the main application card.
In the end, it is really about what your users prefer, but remember a lot of them might prefer what they know, even if it is not a better solution. You have to find a balance, and if your implementation rocks, then eventually they will want your approach to the problem to be used in other applications.
A perfect example of this is tabbed browsing, as opposed to multiple windows. Personally, I can't imagine going back to multiple-window browsing now that I have become accustomed to browsing tabs, but at one point in time, multiple windows was the only game in town.
In the end, if you find out you made the wrong choice, keep you code clean enough to easily implement with either solution. As long as your configuration screen is just a plain JPanel (or wrapped in just a JPanel), it shouldn't be very hard to do.

here is a class that does just this kind of thing:
http://tus.svn.sourceforge.net/viewvc/tus/tjacobs/ui/dialogs/ParamDialog.java?view=log

you have to look at the ApplicationListener interface, especially at the 'handlePreferences' method of that interface.

Gui - Best way to navigate between windows?

I try to build a gui (Swing) for a simple java application. The application should have a start window like a menu. From there I would like to navigate to several other windows.
My question is what is the best-practice to achieve such a navigation? Should I build several JFrames and switch the visibility of them on/off when navigating OR should I better have one JFrame and add/remove JPanels in this single frame to navigate between the windows?
Thanks.

I recommend
Do not do a MDI application with sub-frames like those found in the old Windows days. They suck as they make the matter confusing.
Do design a tabbed interface. The welcome page/menu will be displayed on a first tab that is always created on the start.
All cool kids do that nowadays:
Visual Studio
Eclipse
Firefox

If each of your windows correspond to different task (possibly nested), you could present your application as a SDI, with on the left a task panel like:
Each of the task would display one JFrame with the associated window.
Other solution: a table of content like this picture on the left side
(note: it actually also displays a task panel in this example on the bottom right)

Multiple JFrames sounds like a better idea to me. Much more OO.

You must find a balance between these goals:
Not too many things in one "window"
The user must quickly be able to find the correct window to do the next step of work
All relevant information must be visible at any time
Eclipse solves this by creating many small editors where each editor shows some specific information and allows to modify it. Editors are then arranged within one OS window in tabs and "views". A view is always completely visible and they can be arranged. Think of a view as a way to cut an existing editor in half (horizontal or vertical) and then being able to replace one of the halves with another editor. Between each half, you have a splitter so you can adjust the sizes.
Arrangements of views are then saved in "perspectives".
This allows every user to create a perspective which contains all the necessary editors at the same time, arrange them as they need it and work effectively.