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Editorial Team
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Asked: 2026-05-21T05:55:29+00:00

I’ve written a simple application that works with database. My program have a table

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I’ve written a simple application that works with database. My program have a table to show data from database. When I try to expand frame the program fails with OutOfMemory error, but if i don’t try to do this, it works well.

I start my program with -Xmx4m parametre. Does it really need more than 4 megabytes to be in expanded state?

Another question: if I run the java visualVM I see the saw-edged chart of the heap usage of my program while other programs which is using java VM(such as netbeans) have more rectilinear charts. Why is heap usage of my program so unstable even if it does nothing(only waiting for user to push a button)?

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  1. Editorial Team

    You may want to try setting this value to generate a detailed heap dump to show you exactly what is going on.

    -XX:+HeapDumpOnOutOfMemoryError

    A typical “small” Java desktop application in 2011 is going to run with ~64-128MB. Unless you have a really pressing need, I would start by leaving it set to the default (i.e. no setting).

    If you are trying to do something different (e.g. run this on an Android device), you are going to need to get very comfortable with profiling (and you should probably post with that tag).

    Keep in mind that your 100 record cache (~12 bytes) may (probably) is double that if you are storing character data (Java uses UCS-16 internally).

    RE: the “unstability”, the JVM is going handling memory usage for you, and will perform garbage collection according to whatever algos it chooses (these have changed dramatically over the years). The graphing may just be an artifact of the tool and the sample period. The performance in a desktop app is affected by a huge number of factors.

    As an example, we once had a huge memory “leak” that only showed up in one automated test but never showed up in normal real world usage. Turned out the test left the mouse hovering over a tool tip which included the name of the open file, which in turn had a set of references back to the entire (huge) project. Wiggling the mouse a few pixels got rid of the tooltip, which meant that the references all cleared up and the garbage collector took out the trash.

    Moral of the story? You need to capture the exact heap dump at time of the out-of-memory and review it very carefully.

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