http://dev.processing.org/source/index.cgi/trunk/processing/core/src/processing/core/PApplet.java?view=markup

in PApplet:6605 (r3047) it uses
Class c = Class.forName(name);

This is old style coding, and now following is propper
Class c = Thread.currentThread().getContextClassLoader().loadClass(name);

because the first one will not work in the situation where there are some
class loaders.

we'll only be making the switch on this if we decide to give up support for
Java 1.1 permanently. for the time being, it hasn't caused any reported
problems.