Java source files have a .java extension. When you compile this code with a java compiler, the resulting byte code or object code is stored in a file that has the same name, but a .class extension; this extension indicates that the file is a java executable module. The object code stored in .class files can be executed using a standard java interpreter, including the one that is packaged with MATLAB.

Note that .class files are platform independant. This is because the Java Virtual Machine is identical on all platforms that support java. So the object code created using the java compiler on a UNIX platform for example, would run just as well on a PC.