Compiles and runs a plugin. Requires that ImageJ be running on a Java Virtual Machine that includes the javac compiler.

Runs a plugin if the name of the selected file ends in “.class”, otherwise tries to compile a java file. Hold down the Alt key while running this command to have the javac compiler generate the debugging infomation required for monitoring variables using debuggers such as NetBeans and Eclipse. You can also use Edit > Options > Compiler to create .class files for debugging. There, you can also select the Java version of the .class file.

Use an underscore in the filename (and the class name) if you want that ImageJ loads your plugin automatically on startup (or when selecting Help > Update Menus). The underscore character will be converted into an space in the Plugins menu, e.g. Example_Plot.class will appear as menu item “Example Plot”.

If your plugin accesses a package contained in a jar file located in the plugins folder, this jar file must not contain an underscore.

Javac is included with the Windows and Linux versions of ImageJ that come bundled with a Java runtime. It is also included with Mac OS X Java.

Users of Sun's Java 2 SDK (Software Development Kit) for Windows, Linux and Solaris must add tools.jar to the command line that runs ImageJ.

Here is an example Windows command line for running ImageJ using the Java 2 SDK (aka JDK):

java -mx100m -cp ij.jar;C:\jdk1.4\lib\tools.jar ij.ImageJ

It assumes the Java 2 SDK is installed in C:\jdk1.4.

On a Unix system, the command would look something like this:

java -mx100m -cp ij.jar:\usr\local\jdk1.4\lib\tools.jar ij.ImageJ

The -mx100 options specifies that ImageJ can use up to 100MB of RAM. To avoid virtual memory thrashing, this value should not be set to more than 2/3 of available RAM (e.g. -mx170m on a 256MB machine).

On Windows, you can create a double-clickable shortcut that uses Java 2 to run ImageJ:

1. Right-click on the desktop and select New→Shortcut from the menu
2. Enter:
   javaw -mx100m -cp ij.jar;C:\jdk1.4\lib\tools.jar ij.ImageJ as the “Command line”; click “Next”
3. Enter a name for the shortcut (e.g. “ImageJ”); click “Finish”
4. Right-click of the newly created shortcut and select Properties from the menu
5. Click on the Shortcut tab
6. Enter the path to the ImageJ folder (normally C:\ImageJ) in “Start in”; click “OK”

“javaw” is a variation of the java command that runs Java applications without a DOS windows.