Garbage collection error in Kathy SCJP1.5 book

[krishna bulusu]

Hi,

The following example given in the Garbage collection topic in SCJP 1.5 book by Kathy.

class GarbageTruck {
public static void main(String [] args) {
StringBuffer s1 = new StringBuffer("hello");
StringBuffer s2 = new StringBuffer("goodbye");
System.out.println(s1);
// At this point the StringBuffer "hello" is not eligible
s1 = s2; // Redirects s1 to refer to the "goodbye" object
// Now the StringBuffer "hello" is eligible for collection
}
}

I believe, GoodBye object must supposed to be Garbage collected as the s2 refers to Hello object after the line s1=s2?
Please tell me if this is other way around?

[sudipto shekhar]

krishna bulusu wrote:
I believe, GoodBye object must supposed to be Garbage collected as the s2 refers to Hello object after the line s1=s2?

Can you please explain how s2 refers to hello after s1=s2?

[arulk pillai]

No it is not an error.

after s1 = s2, s1 & s2 are pointing to the "goodbye" StringBuffer objects.

The "hello" object has no references pointing, hence eligible for GC.

[sudipto shekhar]

Thank you Mr. Pillai.