About Question enthuware.ocajp.i.v7.2.920 :

[admin]

There is only one variable named obj in the given code and that variable is declared at line //1. So, I am not sure what is the confusion about the variable.
Please remember that variable and the object to which it points are two different things.

[morarumaria1988]

It's clear now, thanks!

[demetrio]

Suppose the question code was (I just added one println line):

public class NewClass {
private Object o;
void doSomething(Object s){
o = s;
//line bellow was added
System.out.println("the second time this line is printed is the exact moment "
+ "when the object created in line 1 can be Garbage Collected"); //line 7
}

public static void main(String args[]){
Object obj = new Object(); // 1
NewClass tc = new NewClass(); //2
tc.doSomething(obj); //3
obj = new Object(); //4
obj = null; //5
tc.doSomething(obj); //6
}
}

Am I right? I mean, the second time line 7 is evoked is the exact moment where the object created in line 1 is eligible for garbage collector, right?

[admin]

Correct.

[qazwsx922]

How do I know line5 makes obj(on line 4) null?,instead of line 1 obj?

I thought line 5 made line1 obj null.

[admin]

The code given in the question is:

Code: Select all

      Object obj = new Object(); // 1
      NewClass tc = new NewClass(); //2
      tc.doSomething(obj); //3
      obj = new Object();    //4
      obj = null;    //5
      tc.doSomething(obj); //6

obj is being reassigned a new Object at //4, that means the statement obj = null; at //5 will cause that Object to lose the reference.