Xplain me plz..

[Nandish KB]

4 Which line of code inserted //Here will free up a single object for garbage

collection?

--------------------------------------------------------------------------------
 
class C { 
 public C i;
} 
 
class MixedUp {     
      public static void main (String [] args) {
       C a = new C();
       C b = new C();
       C d = new C();
       C e = null;
       d.i = a;
       b.i = e;
       a.i = b;
       a = null; 
     // Here    
    }
}

Answers:
1 a.i = null;
2 b.i = a.i;
3 b = null;
4 a = d.i;
5 d.i = b.i;
6 e = null;

Correct Ans: 5

Plz Explain me in detail Y 5 is the correct ans.
Regards,
Nandish
[ September 22, 2004: Message edited by: Barry Gaunt ]

[Mahesh Bhatt]

Hi nandish,

here is the explanation, sorry I cannot give you a pictorial representation here, so it might be a little hard understanding this:

 
class C {
  public C i;
}  
 
class MixedUp {   
        public static void main (String [] args) {   
          C a = new C();  // a new object is created with "i" inside it and  a  points to it.
          C b = new C(); // a new object is created with "i" inside it and  b  points to it.
  
          C d = new C(); // a new object is created with "i" inside it and  d  points to it.
     
          C e = null; // a local reference variable is created and initialized with null
     
          d.i = a;  // the "i" inside d refers to the object, to which "a" point... (kind of linking happening here)   
          b.i = e;  // now here i inside b points to where e points that's null.  
          a.i = b;    // here i inside a points to where b points 
          a = null;    // now a points no where 
          // Here       
 }
}
 

if you try to make a pictorial representation of this explanation step by step I am sure you would get this concept very much clear, I do it, it would even help you in your exam.
[ September 22, 2004: Message edited by: prashant bhogvan ]

[Nandish KB]

Hi Prashant,
Thanx for ur response.Yeah I came to know about it by drawing diagrams as per ur suggestions..

Thanx.