Why declare a reference to an instance of a final class as being final?

Question

What is significance of second line :

public final class A {}
final A obj1=new A();

If A is a already immutable, why would one possibly want to make obj1 final? (just to make it stick to a unique memory reference? ).

Answer 1

final in the first line means that the object is closed for extension...i.e. you can't subclass it.

final in the second line means you can't reassign the variable.

Answer 2

First, A is not immutable of you just declare it final.

Then, final variables cannot be changed. If obj1 is a field this enforces mutability (unlike the final class).

If it is a local variable it means you can safely use it in anonymous classes (otherwise the compiler can't be sure it won't get change sometimes before/while the anonymous class body is executed)