How Can I Dynamically Find and Instantiate Subclasses of a Base Class in Java at Runtime?

Finding Classes that Extend a Base Class at Runtime

In Java, it can be a challenge to dynamically find all classes that extend a particular base class. This article explores a Java coding problem and discusses methods to address it.

The primary question posed is how to dynamically create a list of objects from classes inheriting from a base class (e.g., Animal). The desired approach involves detecting these subclasses automatically during runtime, eliminating the need for manual additions of each new class.

Originally, it was believed that such a feature was not directly supported in Java due to its decentralized structure. However, advancements in the Java ecosystem have introduced libraries that can assist in this endeavor.

org.reflections Library

One notable library is org.reflections. It provides a convenient get method to retrieve subclasses of a given type.

Reflections reflections = new Reflections("com.mycompany");
Set<Class<? extends MyInterface>> classes = reflections.getSubTypesOf(MyInterface.class);

Other Options

In addition to org.reflections, other libraries have emerged that offer similar capabilities. One example is ClassGraph, which provides comprehensive scanning and reflection capabilities.

By leveraging these libraries, developers can dynamically discover and instantiate subclasses, achieving the desired functionality without explicitly maintaining a list of classes. This approach promotes adaptability and allows for seamless integration of new subclasses without manual updates.

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