Question from mock test

[ragi singh]

hi i have a question :-

 

public class CardBoard {

	Short story=200;
	
	CardBoard go(CardBoard cb){
		cb=null;
		return cb;
	}
	
	public static void main(String[] args){
		
		CardBoard c1=new CardBoard();
		CardBoard c2=new CardBoard();
		CardBoard c3=c1.go(c2);
		c1=null;
		//do stuff
		
	}
	
}

now the question is :- How many objects are eligible for Garbage Collection after line //do stuff ?
According to me all the c1,c2 and c3 are eligible for garbage collection . However the answer says only two objects are eligible for garbage collection ie c1 and associated Short object .

[Harpreet Singh janda]

only 2 objects are eligible. Other objects will be still live they will be eligible after the execution exit the Main method (closing braces of Main).

[Minhaj Mehmood]

This question is discussed many times, just give a try to search first then let us know if you still have confusion.


Regard

Minhaj

[Seetharaman Venkatasamy]

ragi singh wrote:
CardBoard go(CardBoard cb){
cb=null;
return cb;
}

you might think that, here you are assigning a null value to cb, so c2 will also eligible to GC. but Java passes the copy of the reference value . so cb and c2 are two different references

[Bejja Hassan]

the reference variable c3 doesn't refer any object since the new key word is not used to instanciate the object.
c2 object is not eligible the GC because the cb object can't make it refer to a different object or null
c1 object is changed to null, and since it holds a short object, it'll too set up to null and these are the objects eligible the GC

[Shanky Sohar]

public class CardBoard {  
   
     Short story=200;  
       
     CardBoard go(CardBoard cb){  
         cb=null;  
         return cb;  
     }  
      
    public static void main(String[] args){  
           
         CardBoard c1=new CardBoard();  
         CardBoard c2=new CardBoard();  
         CardBoard c3=c1.go(c2);  
         c1=null;  
         //do stuff  
           
     }  
       
 } 

lets understand above code by diagram...

        -------------------------
c1------- new CardBoard()       -  
        -  Short                -
        -------------------------


        -------------------------
c2------- new CardBoard()       -  
        -  Short                -
        -------------------------


c3 is a refernce variable so donot care about it.

now c1=null which means


          -------------------------
c1        - new CardBoard()       -  
!         -  Short                -
!         -------------------------
null



        -------------------------
c2------- new CardBoard()       -  
        -  Short                -
        -------------------------

So the object are eligible point by c1 are eligible for garbage collection..

And also remember only objects are eligible for Garbage collection not the refernce variable