Listing all the subclasses of a specific class in Java

Question

How do I list down all the subclasses of a specific class or all the implementers of a specific interface in Java? Using Eclipse, I am able to do so but I want to know how to perform this programmatically? If you have any suggestions, please do put them.

Answer 1

There is a simple library available for this purpose: org.reflections

This will scan your classpath, index the metadata, allow you to query it on runtime and may save and collect that information for many modules within your project.

Using Reflections you can query your metadata such as:

• get all subtypes of some type

• get all types/constructors/methods/fields annotated with some annotation, optionally with annotation parameters matching

• get all resources matching a regular expression

• get all methods with specific signature including parameters, parameter annotations, and return type

• get all methods parameter names

• get all fields/methods/constructors usages in code

You just need to call the following to fulfill your task:

reflections.getSubTypesOf(aClazz))

Hope this helps!!

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Answer 2

This is not possible to do using only the built-in Java Reflections API.

A project exists that does the necessary scanning and indexing of your classpath so you can get access this information...

Reflections

A Java runtime metadata analysis, in the spirit of Scannotations

Reflections scans your classpath, indexes the metadata, allows you to query it on runtime and may save and collect that information for many modules within your project.

Using Reflections you can query your metadata for:

· get all subtypes of some type

· get all types annotated with some annotation

· get all types annotated with some annotation, including annotation parameters matching

· get all methods annotated with some

Source : Stackoverflow

Answer 3

Try with BurningWave core library. Here an example that solves your question:

https://github.com/burningwave/core/wiki/Finding-all-classes-that-extend-a-base-class