Class#isInstance vs Class#isAssignableFrom [duplicate]

Question

Given a Class<?> superType and a Object subInstance, what are the differences between

superType.isInstance(subInstance)

and

superType.isAssignableFrom(subInstance.getClass())

(if any)?

Answer 1

isAssignableFrom also tests whether the type can be converted via an identity conversion or via a widening reference conversion.

    Class<?> cInt = Integer.TYPE;

    Long l = new Long(123);

    System.out.println(cInt.isInstance(l)); // false
    System.out.println(cInt.isAssignableFrom(cInt)); // true

Answer 2

In the scenario, there is no difference.

The difference between both methods are the parameters. One works with object and one with classes:

Class#isInstance(Object)

Determines if the specified Object is assignment-compatible with the object represented by this Class.

Class#isAssignableFrom(Class)

Determines if the class or interface represented by this Class object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specified Class parameter.

Answer 3

isAssignableFrom() will be true whenever the class represented by the class object is a superclass or superinterface of subInstance.getClass()

isInstance() will be true whenever the object subInstance is an instance of superType.

So the basic difference is that isInstance works with instances isAssignableFrom works with classes.

I often use isAssignableFrom if I don't have an instance/don't want to instantiate the class for some reason. Otherwise you can use both.