Implementing a plugin interface

What's a good way of adding a plugin interfac开发者_如何学运维e such that it's possible to have optional components?

I'm aware of the Class.forName() approach (used with JDBC for example) but there is also this approach to dynamic class loading.

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You may have a look at this: http://jpf.sourceforge.net/.

A good approach would be to load jar files in a specified directory at runtime and look if they contain plugin classes. Have a look at this: How to load a jar file at runtime.