How to Check if a Class Object is a Subclass of Another Class in Java

How can I determine if a class is a subclass of another class in Java using reflection?

if (SomeClass.class.isAssignableFrom(SubClass.class)) {
    // SubClass is a subclass of SomeClass
} else {
    // SubClass is NOT a subclass of SomeClass
}

In Java, you can leverage the reflection API to check if a class is a subclass of another class. Unlike direct comparisons for non-derived classes, you can use the `isAssignableFrom()` method to simplify this task. Below, I will explain how to effectively use this method to perform your checks.

Class<?> superclass = List.class;
Class<?> subclass = LinkedList.class;
if (superclass.isAssignableFrom(subclass)) {
    System.out.println(subclass.getName() + " is a subclass of " + superclass.getName());
} else {
    System.out.println(subclass.getName() + " is NOT a subclass of " + superclass.getName());
}

Causes

• Understanding class hierarchies in Java.
• Familiarity with the reflection API and its methods.”

Solutions

• Use the `isAssignableFrom()` method of the Class class to check subclass relationships.
• Avoid manually traversing superclasses unless necessary.

Mistake: Using `instanceof` instead of `isAssignableFrom()`

Solution: Remember to use `isAssignableFrom()` to check class types and hierarchy.

Mistake: Confusing the terms class and object

Solution: Understand that class comparisons require the Class objects, whereas object comparisons use `instanceof`.