Is it possible to get all the subclasses of a class? [duplicate]

Answer 1

you should use Java ServiceLoader that is a builtin class. It is capable of iterating at runtime over all know service (interface) implementations.

If for some reason you don't want it, you can use ClassLoader.getSystemResources() to iterate over all resources; e.g. if you have 6 times the file /META-INF/com.interface you'll get 6 iterations.

Answer 2

Do you want to enumerate classes that implement a particular interface or enumerate classes that derive from some base class? These are two different issues. Both as far as I know would be hard to implement since new implementations can be created/installed on a PC at any time in the future. It sounds like you are trying to create a factory method to instantiate a particular instance and you don't want to hard-code the class name in the code. Usually using a config file that enumerates all the classes that implement the interface is the way to go (or a database can be used). As new classes implement the interface, you add them to the config file and the factory should pick up the new class name.