Inner Class in Java

Question

I was reading about Inner class in Learning Java. I found this code

class Animal{
   class Brain{
   }
}

After compiling, javap 'Animal$Brain' gives output as

Compiled from "Animal.java"class 
Animal$Brain {
    final Animal this$0;
    Animal$Brain(Animal);
}

which explains how the inner class gets the reference to its enclosing instance in the inner class constructor. But when I define the inner class as private like this

class Animal{
   private class Brain{
   }
}

then after compiling, javap 'Animal$Brain' gives the output as

Compiled from "Animal.java"
class Animal$Brain {
    final Animal this$0;
}

So why is the output different? Why is the inner class constructor not shown? In the latter case also, the inner class is getting the reference of enclosing class instance.

Answer 1

Good question. According to this ,

If no options are used, javap prints out the package, protected, and public fields and methods of the classes passed to it

Since you have declared Brain as a private inner class, its default constructor will be implicitly made private and hence it will not be visible outside the Animal class.

Ref: http://docs.oracle.com/javase/specs/jls/se7/html/jls-8.html#jls-8.8.9

Answer 2

By default, javap prints non private members of the classes.

You can use -p option to shows all classes and members.

//javap -p 'Animal$Brain.class'

Compiled from "Animal.java"
class Animal$Brain {
  final Animal this$0;
  private Animal$Brain(Animal);
}