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Java runtime environment control

There are four ways to control Java environment for runtime:

  • _JAVA_OPTIONS environment variable.
  • Command line when running the java virtual machine.
  • Java source code. In this case you must make sure to set the option before it is picked up by whatever subsystem it is intended for.
  • In Java web start you can also use the JNLP file to control the environment passed over to the executing JVM.

Examples of them can be:

  • export _JAVA_OPTIONS='-Dawt.useSystemAAFontSettings=lcd'
  • java -Dawt.useSystemAAFontSettings=lcd [arguments...]
  • System.setProperty("awt.useSystemAAFontSettings","lcd");
  • property name="awt.useSystemAAFontSettings" value="lcd" (under the resources element)

Each of these methods naturally has it’s own advantages and disadvantages. In Java web start you have a hard time controlling the environment variables or the command line but two options (the JNLP file and the source code itself) are still open to you.

Some properties, like the anti-aliasing option, is notoriously bad by default and setting it (as shown above) will give you much better look and feel.

The values of the awt.useSystemAAFontSettings key are as follows:

  • false corresponds to disabling font smoothing on the desktop.
  • on corresponds to Gnome Best shapes/Best contrast (no equivalent Windows setting).
  • gasp corresponds to Windows Standard font smoothing (no equivalent Gnome desktop setting).
  • lcd corresponds to Gnome’s subpixel smoothing and Windows ClearType.

What is the best option to choose? Well – I really don’t know. On my laptop lcd looks best. Let me know about your own experience…

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Switching Java versions on a Debian/Ubuntu system

I recently found some issues with the openjdk Ubuntu/Debian default Java implementation. Specifically I had issues with their web start support (javaws). I found that the Sun implementation of Java did not have such a deficiency and the Sun implementation is available through the regular Ubuntu/Debian package sources. I installed the Sun implementation and wanted to switch the default Java to that version.

So what have I found out ?

When you want to switch to the Sun implementation:

sudo update-java-alternatives --set java-6-sun

When you want to go back to the openjdk implementation:

sudo update-java-alternatives --set java-6-openjdk

Notice that once you do any of the above you leave “auto” mode which means that new installation of Java implementation will not switch your default one. If that is what you want then ok. If not you can return to “auto” mode with:

sudo update-java-alternatives --auto