About Question com.enthuware.ets.scjp.v6.2.189 :

[TwistedLizard]

Option 2:
Non-static inner classes cannot contain static members.

Commentary:
They can if the static variable is also made final.

Is this only for primitive member variables? Attempting to declare a final reference variable in a non-static inner class results in a compiler error, in this case at least:

Code: Select all

import java.util.Date;

class Test{
  class Inner{
    final static Date date = new Date();    //illegal static declaration
  }
  public static void main(String[] args){}
}

[admin]

JLS Section 8.1.3 clearly states:

It is a compile-time error if an inner class declares a member that is explicitly or
implicitly static , unless the member is a constant variable (§4.12.4).

And as per 4.12.4,

A constant variable is a final variable of primitive type or type String that is initialized with a constant expression (§15.28)

So for example, static final String s = ""; compiles but static final String s = new String(); doesn't.

That's explains why your code fails to compile.

[TwistedLizard]

ok. Thanks for your help.