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Java Forum / General / March 2008JLabels Are Big
I'm currently in the process of creating a "tokenized" panel where a formula can be displayed on that panel and the user can select different tokens and add/remove them. Currently, I am using a JPanel and I'm using a JLabel to display and draw the formula text. (One JLabel per token.) The problem I am noticing is that JLabels chew up memory. If 20 or more tokens are created (which is quite possible given the functionality of the application), memory starts loading up and the application bogs down. Does anybody have any alternative suggestions to using a JPanel w/ JLabels. So far I have come up with: 1. Write my own "JLabels" that only provide the functionality I need. The problem is, it seems that a lot of the extra crap comes from Component, JComponent, etc (all the stuff that JLabel needs to draw itself). So, I'm not sure this idea would help anything. 2. I could also write a JPanel of sorts and have it render its text directly in the panel rather than through the JLabels. Then, when the user clicked the JPanel, I would have to do the work to check where the selection is taking place and do all the drawing for line wrapping, selection, key and mouse listeners, etc, etc. This would definitely make things more lightweight in terms of memory, but I'm not sure that this is the best way to go due to the time involved. If anybody has any additional suggestions, I'd appreciate it. Basically, I need to not use as much memory with the JLabels. Thanks > I'm currently in the process of creating a "tokenized" panel where a > formula can be displayed on that panel and the user can select [quoted text clipped - 5 lines] > created (which is quite possible given the functionality of the > application), memory starts loading up and the application bogs down. 20 sounds like a reasonable number of labels. Are you sure the memory is being chewed up by the labels? Have you run a memory profiler to determine this? > Does anybody have any alternative suggestions to using a JPanel w/ > JLabels. So far I have come up with: [quoted text clipped - 14 lines] > If anybody has any additional suggestions, I'd appreciate it. > Basically, I need to not use as much memory with the JLabels. JLabels don't generally use *that* much memory, I think perhaps there is some other issue in your program. > Thanks Good luck, Daniel.  SignatureDaniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/> > noticing is that JLabels chew up memory. If 20 or more tokens are > created (which is quite possible given the functionality of the > application), memory starts loading up and the application bogs down. I agree with Daniel, 20 labels is not a lot. You likely have some other resource issue here. Better fix that first. > 2. I could also write a JPanel of sorts and have it render its text > directly in the panel rather than through the JLabels. Then, when the > user clicked the JPanel, I would have to do the work to check where This is more or less what I would do. Create your own java.awt.Component that just displays what you want. You might be able to subclass Image and then just draw the formula with Graphics2D operations, and then update in the usual way for Images. However, you might check out JEditorPane. It might be possible to compose your formula in HTML, and then just use setText. HTML also might be more portable. JEditorPanes are already editable, so you might be able to leverage that instead of do the all the code for editing from mouse click and keyboard presses yourself. > > noticing is that JLabels chew up memory. If 20 or more tokens are > > created (which is quite possible given the functionality of the [quoted text clipped - 17 lines] > be able to leverage that instead of do the all the code for editing from > mouse click and keyboard presses yourself. I did a little more research. As you have said, 20 labels isn't big and doesn't really affect anything. But, when I get upwards of 100+ labels, I notice a pretty big slowdown. Even then, my JLabels are ~419 bytes in size and, while that is somewhat big, it's not THAT big. I guess I'll start doing some memory profiling to find out where memory is being used up and what's causing the problem. > I did a little more research. As you have said, 20 labels isn't big > and doesn't really affect anything. But, when I get upwards of 100+ [quoted text clipped - 3 lines] > I guess I'll start doing some memory profiling to find out where > memory is being used up and what's causing the problem. You may have lots of previously made objects (labels) laying around taking up memory, and the gc is thrashing trying to find new memory to allocate. If something is holding a reference to those old labels, they'll not be available for garbage collection. When you profile, turn on both object creation and garbage collection monitoring (under "Memory"). That way you'll have the data you need. I'd also turn on Thread Monitoring (under "Monitor") because it sounds a bit more like you have a run-away thread or something. Look at the "generations" column of the memory allocation display. Objects that survive many generations of garbage collection are possibly leaking. If you should have 100 labels but there are 10,000 in memory being held, you definitely have some sort of leak. Looking at the generation number might help you figure out where the leak is. You may have to turn on stack tracing for object creation to figure out exactly where this is. > > I did a little more research. As you have said, 20 labels isn't big > > and doesn't really affect anything. But, when I get upwards of 100+ [quoted text clipped - 21 lines] > have to turn on stack tracing for object creation to figure out exactly > where this is. I'm assuming you're looking at the hprof tool that is supplied with the JVM? (Just making sure.) > I'm assuming you're looking at the hprof tool that is supplied with > the JVM? (Just making sure.) Actually I'm looking at the profiler in NetBeans. Take a look at this, see if it looks like something you'd like to use. NetBeans is an easy download, and you can import any project just by pointing it at the build script and the source file tree. http://www.netbeans.org/kb/60/java/profiler-intro.html Sorry about that, I just assumed you were using an IDE. > > I'm assuming you're looking at the hprof tool that is supplied with > > the JVM? (Just making sure.) [quoted text clipped - 8 lines] > > Sorry about that, I just assumed you were using an IDE. No problem. I am using an IDE - Eclipse. I'll look to see what sort of profiling tools Eclipse may have. If not, I'll check out Netbeans. Thank you for the detailed description on the Netbeans profiling tool. > No problem. I am using an IDE - Eclipse. I'll look to see what sort > of profiling tools Eclipse may have. If not, I'll check out Netbeans. > > Thank you for the detailed description on the Netbeans profiling tool. I don't mean to start any editor wars. I'm sure Eclipse has similar, if not identical, capability. I think NetBeans uses JMX so I its reporting would be exactly the same as any other tool. Please do report back what you find in Eclipse. I'm not up to speed on it, and I'd love to have some info at my finger tips when I start to work on it more earnestly. On Tue, 4 Mar 2008 12:23:50 -0800 (PST), Jason Cavett <jason.cavett@gmail.com> wrote, quoted or indirectly quoted someone who said : >Does anybody have any alternative suggestions to using a JPanel w/ >JLabels. So far I have come up with: This is a trick I learned back in the jdk 1.0 days for speed. You created JPanel like Component that you draw the labels on yourself. You calculate the x,y and use Drawstring, and perhaps some other fancy decoration. When you get a mouseclick you divide x by label width and y by label height to get the label grid indexes. -- Roedy Green Canadian Mind Products The Java Glossary http://mindprod.com Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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