Release memory from Swing components

Ive experiencing memory leak when using swing components in a custom node object.
When I set the node to null or just delete it from my group node the garbage collector kicks in but when I add a swing component the memory clogs up quickly.
Ive been using the code below for adding a swing component:
insert textField = SwingTextField {
columns: 20
borderless: false;
width: beginBalk - 5;
height: 30;
enabled:false;
text: "Sample text";
editable: false;
} into grp.content;
grp is a common Group node and other component are added aswell.
The complete group node is added to another group which if I want to refresh I use:
delete grp from rootGrp.content;
rootGroup is the other group node that is added to a scene.
I works fine without the swing components so it has got nothing to do with other objects in the group.
Hope anyone has the solution for this,

Hi Hugo,
I'haven't got the solution but perharps the way for destructing the SwingComp can be different.
Has I understood the jvm keep object in survival space until it is referenced by the program.
So If you use
delete comp for group.contentthe jvm probably keep a reference on the comp object.
You can try
delete group.content[idx]instead, then you can adjust jvm garbage collection if the problem persists.

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Simple Java question about releasing beans from memory

Hi,
I use many beans in my app. Is there a way to release them from memory, or destroy the object. I feel that its possibly eating my memory up over time. Most of my beans are in page scope. Some are in session scope. So the page scope ones should kill them at the end of execution of the page and the session ones should delete the object from memory when at the last page of the app where session is no longer needed.
Someone mentioed System.exit(1); but I have not found any clear documentation that this will free up the memory that it has used.
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There is no way to explicitly force the memory to be released. The JVM garbage collection will take care of it when more memory is required. The programmer's responsibility is to ensure that there are no remaining references to the object. System.exit() ends the JVM so you do not want to use that. You can call System.gc() to request that garbage collection runs, but the JVM does not guarantee that it will.

Updating Swing components from a different class

I would like to use the JTextArea component in a JFrame to display fast updating text from my application. My application is very simple. When the app launches the GUI is created then my application engine would start processing and displaying text data into the GUI. After reading about Thread safety when using Swing components I concluded it would not be a good idea for my app engine class to update the JTextArea class directly using methods such as .append(String).
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Many Thanks in advance Sean

Hi
Why don't you just implement a basic callback method?
To do this the right way you should probably define a simple Interface that has a public method like updateProcessText(String s). Your swing class then implements this interface, basically forcing it to provide the public method you defined (this is no different than implementing ActionListener, which forces you to define actionPerformed). Secondly modify your processing class, so that it take's a class that implements the interface you just created, as one of the arguments in it's constructor. Lastly assign the argument from your construnctor to a private var - this will enable your processing class to have a handle to your swing class and update it as it pleases.
This might sound very complex, but it's really simple once you've done it once.

Configuring Swing components from a database

Hi All
I'd like to be able to configure Swing components with information from a database e.g. text, color, editability etc. One approach I'm considering is extending existing components such a JTextField and adding a configure() method which takes as a parameter the primary key of the database record containing the config info.
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Trying to understand "thread-safe" w/ swing components

The other day there was a big hullabaloo about some code I posted because I was calling JLabel.setText from a thread that wasn't the ui thread. On the other hand, this thread was the only thread making changes to the JLabel. My understanding is that in any kind of multi-threaded system, if you just have 1 writer / changer, then no matter how many readers there are, this is thread-safe. So why what I was doing not thread safe?
Second question - JLabel.setText() is essentially setting data in the model for JLabel, which then gets picked up and displayed the next time the GUI thread paints it. So if it's not safe to update a JLabel's model, I assume its never safe to update any data that also is being displayed visually. So for instance, if I was showing some database table data in a JTable, I should do the update in the UI thread - probably not. But what is the distinction?
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Edited by: tjacobs01 on Nov 2, 2008 8:29 PM

tjacobs01 wrote:
My understanding is that in any kind of multi-threaded system, if you just have 1 writer / changer, then no matter how many readers there are, this is thread-safe. So why what I was doing not thread safe?This is not true. As I mentioned in that hullabaloo thread, the Java Memory Model allows threads to cache values of variables they use. This means that values written by one thread are not guaranteed to ever be visible to other threads, unless you use proper synchronization.
Take the following example:
import java.util.concurrent.TimeUnit;
public class ThreadExample {
    static class Foo {
        private String value = "A";
        public String getValue() {
            return value;
        public void setValue(String value) {
            this.value = value;
    public static void main(String[] args) {
        final Foo foo = new Foo();
        Thread writer = new Thread() {
            @Override
            public void run() {
                try {
                    TimeUnit.SECONDS.sleep(1);
                    foo.setValue("B");
                } catch (InterruptedException e) {
                    e.printStackTrace();
        Thread reader = new Thread() {
            @Override
            public void run() {
                try {
                    TimeUnit.MINUTES.sleep(1);
                    System.out.println(foo.getValue());
                } catch (InterruptedException e) {
                    e.printStackTrace();
        writer.start();
        reader.start();
}Here two different threads both access the same Foo instance, which is initialized with a value of "A". One thread, the writer, sleeps one second, and then sets foo's value to "B". The other thread, the reader, sleeps one minute (to avoid race conditions) and then prints foo's value to System.out. It may seem obvious that the reader thread will read the value "B", but this is in fact not guaranteed to be true. The reader thread may never see the value that was written by the writer thread, so it may very well read the old value "A".
(If you run the code you will probably see "B" printed out, but again, this is not guaranteed behavior.)
A simple way to fix this is to synchronize access to the mutable state that the two threads share. For example, change the class Foo to
    static class Foo {
        private String value = "A";
        public synchronized String getValue() {
            return value;
        public synchronized void setValue(String value) {
            this.value = value;
    }It's for this same reason that you often see the use of a volatile boolean as a control flag for stopping threads, rather than a plain old boolean. The use of volatile guarantees that the thread you want to stop actually sees the new value of the flag once it has been set by another thread.
Here is an article that touches some of this stuff:
[http://www.ibm.com/developerworks/java/library/j-jtp02244.html]
I also highly recommend the book "Java Concurrency in Practice" (one of the authors of which, David Holmes, sometime hangs out on the Concurrency forum here, I believe).
Edited by: Torgil on Nov 2, 2008 9:01 PM

Pass Swing components as parameters using RMI

My question is this. Suppose I have a server and a server configuration tool in the same LAN. Suppose I have JPanels assigned to each component of the server as configuration panes. Can I pass the JPanel to the configuration tool from the server depending upon the component selected to be configured.
Simply the question is can I pass a swing component (provided all the components inside this Swing components will be Serializable) as a parameter to another machine using RMI.
Some people say this is not possible because Swing components are not serializable but when I looked in the javadocs most of the Swing components are serializable.
eg. JPanel, JButton, etc.

Hi
I tnxk is possible, because the only condition is the params must be serializable.
If you look at JPanel code you can see :
* JPanel is a generic lightweight container.
* 
* Warning:
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Swing components in applet not working in web browser

Hi Guys,
I've created an applet which makes use of some swing components, but unfortunately, not all of them function properly in my web browser (internet explorer or Mozilla Firefox). Its mainly the buttons; the last buttons works and displays the correct file within the broswer, but the first 5 buttons do not work...
any help please on how I can sort this problem out?
Heres the code for my applet:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.applet.*;
public class MainAppWindow extends JApplet
int gapBetweenButtons = 5;
final JPanel displayPanel = new JPanel(new BorderLayout());
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 button2.addActionListener(
 new ActionListener() {
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 displayPanel.revalidate();
 JButton button3 = new JButton("STACK(ADT)");
 button3.addActionListener(
 new ActionListener() {
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 if(displayPanel.getComponents().length > 0)displayPanel.removeAll();
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 displayPanel.add(new JLabel(new ImageIcon("images/StackADT.jpg")));
 displayPanel.revalidate();
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 button4.addActionListener(
 new ActionListener() {
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 if(displayPanel.getComponents().length > 0)displayPanel.removeAll();
 displayPanel.setBackground(Color.white);
 displayPanel.add(new JLabel(new ImageIcon("images/StacksInTheRealWorld.jpg")));
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 Demonstration app = new Demonstration();
 JPanel appPanel = app.createComponents();//gets the created components from Demonstration application.
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 displayPanel.add(appPanel);
 displayPanel.revalidate();
 JButton button6 = new JButton("Towers Of Hanoi");
 button6.addActionListener(
 new ActionListener() {
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 if(displayPanel.getComponents().length > 0)displayPanel.removeAll();
 TowerOfHanoi app = new TowerOfHanoi();
 JPanel appPanel = app.createComponents();//gets the created components from Towers of Hanoi
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 mainPanel.add(appPanel);
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 displayPanel.add(mainPanel);
 displayPanel.revalidate();
 //adding buttons to the buttonPanel.
 buttonPanel.add(button1);
 buttonPanel.add(button2);
 buttonPanel.add(button3);
 buttonPanel.add(button4);
 buttonPanel.add(button5);
 buttonPanel.add(button6);
 JPanel p = new JPanel(); // Used so that the buttons maintain their default shape
 p.setBackground(Color.white);
 p.add(buttonPanel);
 holdingPanel.add(p,BorderLayout.WEST);
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 mainPanel.add(holdingPanel,BorderLayout.CENTER);
 //indent mainPanel so that its not touching the applet window frame.
 mainPanel.setBorder(BorderFactory.createEmptyBorder(10,20,10,20));
 mainPanel.setBackground(Color.white);
 mainPanel.setPreferredSize(new Dimension(850,600)); //size of applet window
 mainPanel.setOpaque(false); // Needed for Applet
 this.setContentPane(mainPanel);
}

Thanks for the response. I don't quite understand what you're talking about though. I have, in my humble knowledge, done nothing with packages. I have put the applet class (WiaRekenToolActiz.class is the applet class) in the jar file wia_actiz_archive.jar. From what I read on the tutorial, java looks for the applet class in all the jar files specified. Since I put my CODEBASE as the main url, I thought it baiscally didn't matter where you out the html file.
I shall include the complete html page complete with applet tag to perhaps illuminate a bit more what I mean...
<html>
<head>
<title>Wia Rekenmodule hello!</title>
</head>
<body bgcolor="#C0C0C0">
<applet
CODEBASE= "http://www.creativemathsolutions.nl/test"
ARCHIVE= "Actiz/wia_actiz_archive.jar, Generic/wia_archive.jar"
CODE="WiaRekenToolActiz.class"
WIDTH=915 HEIGHT=555
>
<PARAM NAME = naam VALUE = "Piet Janssen">
<PARAM NAME = gebdag VALUE = "01">
<PARAM NAME = gebmaand VALUE = "06">
<PARAM NAME = gebjaar VALUE = "1970">
<PARAM NAME = geslacht VALUE = "man">
<PARAM NAME = dienstjaren VALUE = "10">
<PARAM NAME = salaris VALUE = "56500">
<PARAM NAME = deeltijdpercentage VALUE = "100">
<PARAM NAME = accountnaam VALUE = "Zorginstelling 'De Zonnebloem'">
</applet>
</body>
</html>

I can't use swing components in my applets

When I write an applet without any swing components, my browser never has any trouble finding the classes it needs, whether they're classes I've written or classes that came with Java. However, when I try to use swing components it cannot find them, because it is looking in the wrong place:
On my computer I have a directory called C:\Java, into which I installed my Java Development Kit (so Sun's classes are stored in the default location within that directory, wherever that is), and I store my classes in C:\Java\Files\[path depends on package]. My browser gives an error message along the lines of "Cannot find class JFrame at C:\Java\Files\javax\swing\JFrame.class"; it shouldn't be looking for this non-existent directory, it should find the swing components where it finds, for example, the Applet class and the Graphics class.
Is there any way I can set the classpath on my browser? Are the swing components stored separately from other classes (I'm using the J2SE v1.3)?
Thanks in advance.

Without having complete information, it appears that you are running your applets using the browser's VM. Further, I assume you are using either IE or Netscape Navigator pre-v6. In that case, your browser only supports Java 1.1, and Swing was implemented in Java 1.2. You need to use the Java plug-in in order to use the Swing classes (see the Plug-in forum for more information), or else download the Swing classes from Sun and include them in your CLASSPATH.
HTH,
Carl Rapson

Showing swing components in the palette og jdeveloper

hello, I have found a problem with jdeveloper, as a user uses jdeveloper since 2 years I have never found a problem like this. (IDE problem).
like habitude I created a simple java project which contains a jframe and an entry class (main class), but when I try to drag and drop from the component palette somes swing components I didn't find
the page of swing components ( I found in the components palette just "my components" page in the jcombobox selection category). this problem will delay a big project and causes big problems
please any person who know some things help me as soon as possible.
Best Regards.

Check this post -
showing palette containing JButton,JLabel,JPanel ... components

Multifont output in Swing components

Hi there,
though I'm not new to Java but I'm new to displaying different fonts in Swing components.
I have an Swing-based application which is running on a Terminal Server. It works fine for Central, Western und Northern Europe. The next
country to roll out is Greece. So what does a greek user see on his monitor when he uses his greek keyboard?
I am writing a test app where I type german text into a JTextField and want to get e.g. the greek representation in another JTextField. How can I achieve this? Converting the bytearray with Cp1253 did not work
Can anybody give me a hint?
Thanks
Dierk.

as I wrote, it is a test app to learn how I get greek
fonts on the screen. Of course the real app is used by
greek users who put greek text into the system. In the
system we do not use resource bundles as the GUI texts
are stored in the database. It is a CMS for product
information in different languages.Ah, I see... mind you, I don't think your German text would have a great deal of Cyrillic characters in them, right? Still, it's only a test! ;-)
Now what I'm doing to get my german text in greek
letters is this:
utf8Bytes =
= getorigTextField().getText().getBytes("UTF16");
isr = new InputStreamReader(new
w ByteArrayInputStream
(utf8Bytes), "Cp1253");
As far as I understand, the InputStreamReader gives
the translation
of my german letters in the encoding of CP1253
(Windows Greek). That
means the unicode characters change into the ones of
the greek language
so I should be able to show them in a Swing component.This is where your problem is. Java's Strings will always be in UTF-16 when they are held internally. So anything within a textfield is going to be UTF-16 no matter what you do with it.
The line you think is converting to Cp1253 is actually trying to convert from Cp1253 to UTF-16.
Hopefully this is the reason your characters aren't appearing - the unneeded conversion above could be mashing them. Instead, you need expect everything to always be in UTF-16, and to expect to display in it (don't worry, it handles any character you can throw at it, let alone Greek). So then it all comes down to the font you're using.
I'm not too sure of the name of the Windows default Cyrillic font, but that would be a logical starting point.
Hope that helps!
Martin Hughes

Swing Components not displaying in a JFrame

Hi,
I have a JFrame with a couple of JLabels, JButtons etc. and a Choice Combo Box
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Does anyone know how i can fix this please?
here is my code
import java.awt.*;
import java.awt.event.*;
import java.lang.*;
import java.awt.Image.*;
import java.io.*;
import java.net.*;
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thank you in advance
Ivo

for future reference
i was able to fix this by adding
super.paint(g);in the first line of my paint method
Ivo

Issue viewing Swing components

I currently am able to compile, but not view Swing components. I am running Windows Media Center Edition with Radeon X300 graphics card. Swing programs execute but I only see the border window with only grey content inside. I have 1gb of memory and have tried running very small applications with the same effect. Does Java not support my OS? Any ideas?

Some sample code follows that doesn't work for me
At odd times I can see some of the swing applications I try to run, but it isn't consistent. This makes me think it is a memory problem, but I'm not sure. The following application takes 19,040 K with 373688 K available physical memory.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class DefaultButton {
public static void main(String args[]) {
Runnable runner = new Runnable() {
public void run() {
JFrame frame = new JFrame("DefaultButton");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new GridLayout(2, 2, 10, 10));
JButton button1 = new JButton("Text Button");
button1.setMnemonic(KeyEvent.VK_B);
frame.add(button1);
Icon warnIcon = new ImageIcon("Warn.gif");
JButton button2 = new JButton(warnIcon);
frame.add(button2);
JButton button3 = new JButton("Warning", warnIcon);
frame.add(button3);
String htmlButton = "<html>HTML Button " +
"Multi-line";
JButton button4 = new JButton(htmlButton);
frame.add(button4);
JRootPane rootPane = frame.getRootPane();
rootPane.setDefaultButton(button2);
frame.setSize(300, 200);
frame.setVisible(true);
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How to improve the Performance of Swing Components

Hi
I have developed a GUI Framework with Swing components. I observed that when number of components are more, the GUI is slow. Could anybody suggest me the ways to improve the performance of Swing Components
Thanks

Hi There - I haven't found issues so far with the speed of the GUI building, it seems fast when compared with .NET applications
Are you doing any database querying on form load? This can slow down the loading of the GUI, I use persistence in an application and before the GUI is shown the persistence unit logs in to the database and registers itself - it does take 2/3 seconds to register and complete whatever it does before the form builds and shows
Also check if you are loading/using any network based files on form load, this can also slow down the building considerably as well. Apart from that it's hard to say where your issue may lie apart from removing controls and checking build speed until you find the one that's slowing it down (not a good approach though) I sometimes had to load csv files from a network drive and if the file server is slow or LAN speed isn't great this can also cause a delay, hope you find it.....

PS Touch Android does not release memory when closed.

I have to force closure with Task Manager on my Samsung Note 2 running JB 4.1. Why and when will it be fixed?

Hi Ignacio,
Sorry for the lack of information - I had typed more complete description, but had trouble posting it.
The app is installed on a Samsung Galaxy Note 2 phone that is running Jellybean 4.1.1.
The only way I can see to exit the application is by using the "back" soft key under the screen on the right. Some apps have an "exit" choice under the "menu" soft key, but that key is not active with PSTouch.
I see the same issue with Google Chrome. The menu key is active with this app, but it does not have an "exit" choice.
With both these apps, I have to go to the "Active Apps" tab of the Task Manager to release memory.
There is one difference with PS Touch. Google Chrome always starts the same way whether or not I release it's memory. With PS Touch, if I release memory after closing with the back key, the next time I start it I get an initial royal blue screen with the PS Touch icon in the middle followed by a second screen with a menu in the middle titled "New Project From". If I exit at that point, it takes two presses of the back key to first close the menu and then exit the program and return to a home screen. If I do not release memory, the next time I start PS Touch, it goes directly to the second screen, but without the "New Project From" menu.
I hope this gives you the information you need.
Pete

Developing new Swing Components - Visibility problems with UI classes

I was wondering if anyone out there had run into the following problems when developing new Swing components. If so it might be worth banding together and putting pressure on Sun to fix them. However, if no one else develops new Swing components then I guess I'm just a lone voice...
I have been writing a new dockable toolpanel Swing component and when it came to implementing the UI manager I was unable to access many of the standard features in basic and metal LAFs because they had been made package protected. This forced me to reimplement quite a bit of existing code which took time as well as being bad practice.
While in some cases I can understand this from a security POV I am pretty sure that in this case it is the result of lazy programming practice. Appart from basic architectural reasons for this I have noticed a trend where newer code seems to suffer from this more than the original code. The practice of using package protection reminds me of C++ style coding, or just that of an inexperienced developer who does not understand the need to code for extensibility.
An additional problem arises because the Security manager stops you cheating the system by putting new classes into the javax.swing.plaf... package structure. Thus the only way to solve this nicely is a proper fix.
This would entail going through all the UI PLAF classes and rationalizing the visibility to either public or protected as appropriate. Really there should be minimal use of package protection unless it is vital for security concerns.
Some Examples (there are many more):
javax.swing.plaf.basic.LazyActionMap
javax.swing.plaf.basic.BasicBorders.RolloverMarginBorder
javax.swing.plaf.basic.BasicBorders.SplitPaneDividerBorder (why are just these two classes package protected when all the others are public?)
javax.swing.plaf.metal.MetalUtils
javax.swing.plaf.metal.MetalBumps
Anyway, I am happy to give advice to other poor saps who wind up fighting the UI manager but it would be better if we could get Sun to sort out this mess (after all they created it).
Cheers, Lewis

It may be more a case of creating new Swing components and trying to provide support for all the standard LnFs.
This is very awkward although you can sometimes achieve what you want by borrowing resources from UIManager (a border here, an icon there etc.).
Essentially the problem is that Swing is designed to have new components added to it but the standard LnFs aren't quite so accommodating!

Release memory from Swing components

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