constructors with inner classes.

[Rajani Sudhakar]

I was stuck up at the following question from one of the mock exams.

 //Contents of file A.java 
public class A
{
    A()
    {
        class B
        {
            {
                System.out.println("I am in no-argconstructor");
            }
        }
    }
 
    A(int i)
    {
        class B
        {
            {
                System.out.println("I am in the arg constructor");
            }
        }
        new B();
    }
}
  
class C
{
    public static void main(String[] args) 
    {
        A a = new A(1);
    }
}

Which of the following are true

1. A.java cannot be compiled. Duplicate defination of inner class B.

2. A.java compiles without any error. An attempt to run C as an application will cause runtime linkage error. Duplicate definations of inner class B are found

3. Only one class file corresponding to the inner class B is created in the file system.

4. Two class files corresponding to both inner classes (B) is created in the file system.

5. The classes compile cleanly and on running C as an application causes "I am in the arg constructor" to be printed on the console

Corredct Answer : 4 and 5.

I am satisfied with option 5.
Coming to option 4, the main method has the code A a = new A(1);
which executes the following code:

A(int i)
{
    class B
    {
        {
            System.out.println("I am in the arg constructor");
        }
    }
    new B();
}

So how two class files corresponding to both inner classes (B) are created in the file system ?

Thanks in advance,
Rajani.

Edited by Corey McGlone: Added CODE Tags and Reformatted Code for Readability.
[ June 07, 2004: Message edited by: Corey McGlone ]

[Corey McGlone]

Just because a chunk of code is not executed does not mean it is not compiled. All of the code is compiled - both constructors. As each constructor contains a local class, a class file is generated for each local class. If you compile this code, you'll find that the following class files are generated:

A.class
A$1B.class
A$2b.class
C.class

Therefore, option 4 is correct.

However, this will not appear on the SCJP exam.

[Rishi Tandon]

It Should be :

A.class
A$1$B.class
A$2$B.class
C.class