How many objects are available for garbage collection after the following code is runned?

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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;
	}
}

What I have tried:

According to me all 3 objects c1,c2,c3 must be available for garbage collection as c2 is set to null in go() and it's reference is passed to c3 thus, both refer to null and in the end c1 is also made to refer to null.

Posted 1-Nov-17 23:05pm

Member 13409417

Updated 1-Nov-17 23:53pm

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Mehdi Gholam · Answer 1 · 2017-11-01T23:29:00

Solution 1

After the main() code is run all objects are available for garbage collection.

Garbage collections occur when the JVM hits memory limits, not necessarily immediately after a method completes.

Setting an variable to null may not put that object up for garbage collection, garbage collection checks for "actively referenced" objects throughout the memory.

Posted 1-Nov-17 23:29pm

Mehdi Gholam

Comments

Member 13409417 2-Nov-17 5:48am

I am asking here which CAN be available for garbage collection

CPallini · Answer 2 · 2017-11-01T23:43:00

Solution 2

Uhm....
Try:

Java

  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;
    System.out.println(c2.story);
  }
}

Hint: Java parameters are always passed by value.

Posted 1-Nov-17 23:43pm

CPallini

Comments

Member 13409417 2-Nov-17 5:53am

Please elaborate your solution,

CPallini 2-Nov-17 6:46am

The method go doesn't change c2, because the latter is passed by value.