The Java ClassLoader is a crucial, but often overlooked, component of the Java run-timesystem. It is the class responsible for finding and loading class files at run time. Creating yourown ClassLoader lets you customize the JVM in useful and interesting ways, allowing you tocompletely redefine how class files are brought into the system.
http://www.panix.com/~mito/articles/articles/classloader/j-classloader-ltr.pdf
