Enthuware

An object should be eligible for garbage collection only when his reference becomes pointing to null ?

In general, if there are no references pointing to an object then it is eligible to be garbage collected. But it is a bit more complicated than that. Please go through the following links to understand better:
http://beginnersbook.com/2013/04/java-g ... ollection/

http://www.oracle.com/webfolder/technet ... index.html

Yes. The process is called as Garbage Collection. In this process compiler identifies the objects which are in use and which are not, and deletes the unreferenced objects that is no longer referenced by any part of program.

I would like to suggest refer below resource to understand garbage collection better,

https://www.flowerbrackets.com/garbage- ... n-in-java/

After line 10? Why not in line 10?

Only when the execution of the line is completed, can its effect be seen. So, the object can't be GCed, while line 10 is being executed. Thus, "after" and not "in".

Sorry, but and the line 6?
(I understand what you said about line 10.. )

I am not sure what is your question about line 6. Can you be a bit more clear?

In the following code, after which statement (earliest), the object originally held in s, may be garbage collected ?

1. public class TestClass{
2. public static void main (String args[]){
3. Student s = new Student("Vaishali", "930012");
4. s.grade();
5. System.out.println(s.getName());
6. s = null;
7. s = new Student("Vaishali", "930012");
8. s.grade();
9. System.out.println(s.getName());
10 s = null;
}
}


6. s = null; //right answer
10 s = null;//to me, this answer is correct too

The problem statement is asking about "object originally held in s". This object is eligible for gc after 6.

Generally, an object becomes eligible for garbage collection in Java on following cases:

* Any instances that cannot be reached by a live thread.
* Circularly referenced instances that cannot be reached by any other instances.
* If an object has only lived weak references via WeakHashMap it will be eligible for garbage collection.
* The object is created inside a block and reference goes out scope once control exit that block.