Question

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At runtime, find all classes in a Java application that extend a base class

I need to get list of all the classes (child) which extends a particular class (parent) and then create an instance of them all.

how should I do this in Java?

Answer 1

I would use http://code.google.com/p/reflections/

Using Reflections you can query your metadata such as:

• get all subtypes of some type
• get all types/methods/fields annotated with some annotation, w/o annotation parameters matching
• get all resources matching matching a regular expression

This can be used in an indexed or cached mode. As @Jagger suggests, a brute force search of every class is relatively slow. You can also limit the search by package e.g. com.mycom.*