anglefire.com question

[Shiva Mohan]

Read the following code excerpt carefully. //Contents of file A.java public

    
class A
{
        A()
        {
                class B
                {
                        {
                                System.out.println("I am in no-arg constructor");
                        }
                }
        }
 
        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
Answer are 4 and 5.

6.My question is when I run the program in the command line and listed how many class files are there? to get the answer 4.I got only one class file created.But here,how come the answer �Two class files corresponding to both inner classes (B) is created in the file system.�-is coming?Can anyone please explain?

[peter cooke]

the inner "B" classes. Ok You have defined one B class definition. the sections of code

  
class B { 
     { 
         System.out.println("I am in no-arg constructor");
     } 
}  

and

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

are anonymous inner classes that extend from B.

Read inner classes from thinking in java.

[Barry Gaunt]

Please can you tell us the exact url to these angelfire.com questions?

[Shiva Mohan]

I am sorry to get back this late.
The exact URL is
http://www.angelfire.com/or/abhilash/Main.html

Over there,we can find 9 quizes.

[Shaan Shar]

class C{
       public static void main(String arg[]){
           [B]A a = new A(1);[/B]
       }
}

Then you will get output as

"I am in the arg constructor"

and if we are using class C as follows:

class C{
       public static void main(String arg[]){
           [B]A a = new A();[/B]
       }
}

this time no output is coming instead of
"I am in no-arg constructor"

Why this is coming so???
Should we discuss this in same thread or should we start a new thread...
??
[ July 25, 2006: Message edited by: Ankur Sharma ]

[Neelesh Bodas]

Because the no-arg constructor of class A doesnot create any instance of inner class B.

[Barry Gaunt]

Because the printing of the "I am in the (no)-arg constructors" messages are not in the (no)-arg constructors! They are in instance initialization blocks of the constructors' local inner classes.

I was going to edit this to add what Neelish wrote, but I need not bother now.
[ July 25, 2006: Message edited by: Barry Gaunt ]

[Shaan Shar]

Originally posted by Barry Gaunt:
Because the printing of the "I am in the (no)-arg constructors" messages are not in the no-arg constructors! They are in instance initialization blocks of the constructors' local inner classes.

Oops...... I missed this line...

[B]new B();[/B]

Well Thankx for reminding this line...