GC doubt

[dolly shah]

Object a = new Object();
Object b = new Object();
Object c = new Object();
Object d = new Object();
d=c=b=a;
d=null;
How many objects are eligible for GC?i think only one object but answer is 3 objects.
GC related questions are too tricky. I always give wrong answer. Can anyone please clear my doubt?

[V Gala]

Object a = new Object(); //object 1
Object b = new Object(); //object 2
Object c = new Object(); //object 3
Object d = new Object(); //object 4

d=c=b=a;
d=null;

d=c=b=a;
after this statement a,b,c and d all are pointing to a object 1 since a value has been assign to b,c and d now there are no variable pointing to object 2,object 3 and object 4

d has been assign to null
byt a is still pointing to object 1

[Onkar Joshi]

Originally posted by dolly shah:
Object a = new Object();
Object b = new Object();
Object c = new Object();
Object d = new Object();
d=c=b=a;
d=null;
How many objects are eligible for GC?i think only one object but answer is 3 objects.
GC related questions are too tricky. I always give wrong answer. Can anyone please clear my doubt?

When "d=c=b=a" is executed, d,c,b all take the value of a and the Objects they earlier referred to become eligible for garbage collection. "d=null" does not make any difference since c,b and a will still refer to the object originally referred to only by a.

[Burkhard Hassel]

Wanna try for yourself?

class MyObject extends Object {
String s;
 
MyObject(String s) {
this.s = s;
}
 
public static void main(String[] args) {
Object a = new MyObject("a");
Object b = new MyObject("b");
Object c = new MyObject("c");
Object d = new MyObject("d");
d = c = b = a;
d = null;
System.gc();
System.out.println("main ready");
}
 
public void finalize() {
System.out.println("finalizing " + s);
}
}

Yours,
Bu.

[Bert Bates]

fyi,

you probably won't see a line of code like this:

a = b = c = d;

on the real exam - but it's still interesting to discuss how this line of code works.

[dolly shah]

Thanks Hassel, I got it.