In Java, can I use a primitive type literal or type variable in an instanceof expression?

Question

Can I use a primitive type literal or type variable in an instanceof expression?

class MyClass {
    {
         boolean b1 = null insta         


        

Answer 1

Nope, because of type erasure. An instance of MyClass doesn't actually know what T is.

You need to have an instance of Class. Then you can use the isInstance method. One way of doing that is to specify it in the constructor:

class MyClass
{
    private Class clazz;

    MyClass(Class clazz)
    {
        this.clazz = clazz;
    }

    // Now you can use clazz to check for instances, create new instances ect.
}

For the second one, the problem is the first operand, not the second. The primitive value itself isn't an instance of Integer; the boxed version is:

Object obj = 2;
boolean b2 = obj instanceof Integer;

Whenever you've got a genuine primitive value, you'll already know the type so making a dynamic type check doesn't make much sense.