Possible Duplicate:
How do I programmatically compile and instantiate a Java class?
How to create a new java class at runtime?
Possible Duplicate:
How do I programmatically compile and instantiate a Java class?
How to create a new java class at runtime?
Use
Class<?> ClassLoader.defineClass(String name, byte[] b, int off, int len, ProtectionDomain protectionDomain)
The problem is that this method is protected. So, you should extend class loader with your own class and call this method from there.