Garbage Collection

[Roll]

Q]Which is the earliest line in the following code after which the object created on the line marked(0) will be a
candidate for being garbage collected, assuming no compiler optimization are done?
public class Q76a9 {
static String f() {
String a = "hello";
String b= "bye"; //0
String c = b + "!"; //1
String d = b;
b = a; //2
d = a; //3
return c; //4
}
public static void main(String args[]) {
String msg = f();
System.out.println(msg); //5
}
}
A)The line marked(1)
B)The line marked(2)
C)The line marked(3)
D)The line marked(4)
E)The line marked(5)
Is it line3) because line0) hets garbage collected after line2).
So, i think c) should be correct , but some say's it as B).
Any comments or suggestions?

[paul wheaton]

I'll go with B because in the question it says "Which is the earliest line in the following code after which ..." For me the "after which" makes all the difference.

[Anonymous]

I think it should be C) line three. Here is my reasoning:
The object created in line 0 is a String object containing the letters "bye". Later, the variables b and d both refer to this object. After line two, the variable d still refers to this object, so it can't be garbage collected. After line three, there are no variables referring to that String object, so it could be garbage collected.

[paul wheaton]

Excellent point. You are correct.
Just to mess things up a bit more... The question is obviously designed to find a particular answer. But the question is errant. b references a string constant that is in the String Pool before the program is started. Therefore, it is never garbage collected. This particular example would be better if it had the line b = new String("bye");

[Anonymous]

Can any java Guru explain What is meant BY "assuming no compiler optimization are done?" what implication it has on the Question??
thanks
Sharana

[rajsim]

The smart optimizing compiler could replace the entire
code with the following code without affecting the results.

public class Q76a9 {
static String f() {
return "bye!"; 
}
public static void main(String args[]) {
String msg = f();
System.out.println(msg); 
}
}