更快的是：instanceof或isInstance？

Question

Design questions aside, what performs faster on modern JVMs?

foo instanceof Bar

or

Bar.class.isInstance(foo)

Why?

Answer 1

Class.isInstance is JVM intrinsic. It is compiled to exactly the same sequence as instanceof does (the proof from HotSpot source code: 1 , 2 ). That is, they both are equal in terms of performance.

Answer 2

foo instanceof Bar should be faster.

You can use Bar.class.isInstance(foo) if it's not clear at compile time which class you have.

consider the following:

void test(Object o1, Object o2) {
   o1.getClass().isInstance(o2);
}

In this exsample the JVM decides at runtime which class calls the method. With instanceof this is not possible.

So if you know the class at compile time you should use instanceof