Is there any way other than instanceof operator for object type comparison in java?

Question

I remember reading in some Java book about any operator other than 'instanceof' for comparing the type hierarchy between two objects.

instanceof is the most used and common. I am not able to recall clearly whether there is indeed another way of doing that or not.

Answer 1

You can also, for reflection mostly, use Class.isInstance.

Class<?> stringClass = Class.forName("java.lang.String");
assert stringClass.isInstance("Some string");

Obviously, if the type of the class is known at compile-time, then instanceof is still the best option.

Answer 2

The instanceof operation is the best option for two reasons: 1) It handles subtyping, so if you have an instance of a subclass/subtype you would still get true. 2) It handles null, so null instanceof Class would return false

If you take an object's class and then compare to another class, you're risking taking the class of a null object, and you can't directly get subtyping.

If you work with objects that represent classes, you can use the reflection operations, since instanceof would refer to their own class, Class, rather than to the class they represent.

Answer 3

Yes, there is. Is not an operator but a method on the Class class.

Here it is: isIntance(Object o )

Quote from the doc:

...This method is the dynamic equivalent of the Java language instanceof operator

public class Some {
    public static void main( String [] args ) {
        if ( Some.class.isInstance( new SubClass() ) ) {
            System.out.println( "ieap" );
        } else { 
            System.out.println( "noup" );
        }
    }
}
class SubClass extends Some{}

Answer 4

if ( someClass.isAssignableFrom( obj.getClass() ) )

is equivalent to

if ( obj instanceof Foo )

Use instanceof if the class to be checked against is known at compile time, use isAssignableFrom if it is only known at runtime.