java class object and Types

Question

Given a class

public class A {
  public static int classVal;
}

During run-time, does the type A become a reference to a class Object?

public static void main(String[] args) {
  A a = new A(); 
  A.classVal = 100;
  A.classVal = 200;
}

if A.classVal is a reference to static Class variable, then is A a reference to an Object that represents the class?

does a.getClass() refer to the same object as A?

To clarify

if A.classVal is a reference, and A is nothing more than a name, does a class just become part of a lookup table that uses the class name as a key? I am trying to understand what happens to a class at run-time.

Jon Skeet · Accepted Answer · 2015-07-07 09:16:21Z

3

No, A isn't a reference at all. It's just the class name. A is not an expression in its own right - it doesn't have a value. It can only be part of another expression (like A.classVal or new A()).

answered Jul 7, 2015 at 9:16

Jon Skeet

1.5m893 gold badges9.3k silver badges9.3k bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

beoliver Over a year ago

but when you call new A(), the jvm must know how to look this up - 'name space = A', call = '()'...

Jon Skeet Over a year ago

@ThemanontheClaphamomnibus: I suggest you look at the generated byte code - but none of that means that there is "A reference A". How the JVM handles all of this is an implementation detail.

Akash Thakare · Accepted Answer · 2015-07-07 09:16:38Z

1

First of all,

static refers to the enclosing type and not to the instances

No A does not become a reference to a class Object. Each static member will be created for the type itself and for all the instances of the class the same copy will be used during the execution if you try to access the static member with instance.

It's a way to access the static member in Java with the name of class here A.staticMember.

answered Jul 7, 2015 at 9:16

Akash Thakare

23k11 gold badges64 silver badges89 bronze badges

Comments

tonychow0929 · Accepted Answer · 2015-07-07 09:18:17Z

1

No. A is a class name, but A.class equals a.getClass().

answered Jul 7, 2015 at 9:18

tonychow0929

4664 silver badges11 bronze badges

Comments

Kenny Tai Huynh · Accepted Answer · 2015-07-07 09:24:48Z

1

No, the "A" is just the class. It is not a reference. "a" is an reference object. So, in case you would like to check the class, just compare: a.getClass() vs A.class. They should be equal.

answered Jul 7, 2015 at 9:24

Kenny Tai Huynh

1,6492 gold badges12 silver badges26 bronze badges

Collectives™ on Stack Overflow

java class object and Types

4 Answers 4

2 Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related