logical structure/details of a reference variable and object in the memory?

Question

Let\'s say we have a class:

class Class1
{
   int i = 1;
}

and we have a variable:

Class1 ob1 = new Class1();

Answer 1

Every java object reference knows its class at runtime; this so-called "run-time type information" is used in code like this:

if (obj instanceof class1) {
  // true!
}

You can also access the class of an object through obj.getClass(). This will return class1.class, an object of class Class. See the Object.getClass method.

(Note that if your class is parameterized, as class1, the type of T will not be stored at runtime, due to "erasure".)

I don't know whether the class information is stored with the pointer or with the data; it's probably implementation-specific in the jvm; but it hardly matters from a practical standpoint. (So either answer 1 or 2, or both, is "yes").

The answer to 3 is that, as far as a java programmer is concerned, the run-time type information is encapsulated in an object of class Class. Under the covers, a JVM may implement this in one way or another.