What is the difference between instanceof and Class.isAssignableFrom(...)?

java instanceof reflection
Megamug picture Megamug · Jan 30, 2009 · Viewed 261.6k times · Source

Which of the following is better?

a instanceof B

or

B.class.isAssignableFrom(a.getClass())

The only difference that I know of is, when 'a' is null, the first returns false, while the second throws an exception. Other than that, do they always give the same result?

Answer

Marc Novakowski picture Marc Novakowski · Jan 30, 2009

When using instanceof, you need to know the class of B at compile time. When using isAssignableFrom() it can be dynamic and change during runtime.

Related questions

Is there something like instanceOf(Class<?> c) in Java?

I want to check if an object o is an instance of the class C or of a subclass of C. For instance, if p is of class Point I want x.instanceOf(Point.class) to be true and also …

Read More
Avoiding instanceof in Java

Having a chain of "instanceof" operations is considered a "code smell". The standard answer is "use polymorphism". How would I do it in this case? There are a number of subclasses of a base class; none of them are under …

Read More
Checking if an annotation is of a specific type

I am using reflection to see if an annotation that is attached to a property of a class, is of a specific type. Current I am doing: if("javax.validation.Valid".equals(annotation.annotationType().getName())) { ... } Which strikes me as a …

Read More