Checking if a Java Class is ‘abstract’ Using Reflection

1. Overview

In this quick tutorial, we'll discuss how we can check if a class is abstract or not in Java by using the Reflection API.

2. Example Class

To demonstrate this, we'll create an AbstractExample class:

public abstract class AbstractExample {
    public abstract LocalDate getLocalDate();
    public abstract LocalTime getLocalTime();
}

3. The Modifier#isAbstract Method

We can check if a class is abstract or not by using the Modifier#isAbstract method from the Reflection API:

@Test
void givenAbstractClass_whenCheckModifierIsAbstract_thenTrue() throws Exception {
    Class<AbstractExample> clazz = AbstractExample.class;
 
    Assertions.assertTrue(Modifier.isAbstract(clazz.getModifiers()));
}

In the above example, we first obtain the instance of the class we want to test. Once we have the class reference, all we need to do is call the Modifier#isAbstract method. As we'd expect, it returns true if the class is abstract, and otherwise, it returns false.

4. Conclusion

In this tutorial, we've seen how we can check if a class is abstract or not.

As always, the complete code for this example is available over on GitHub.

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