JVM Class search order

The search order for J2SDK, using the example code above, is:

1. The bootstrap classpath, which is in the sun.boot.class.path property,

2. The extension directories, which is in the java.ext.dirs property,

3. The default system classpath,

4. The current working directory,

5. The myclasses.zip file that is located in the "root" (/) file system,

6. The classes directory in the Product directory in the "root" (/) file system.

http://java.sun.com/j2se/1.4.2/docs/tooldocs/findingclasses.html