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SCJP i need help in garbage collection

 
Greenhorn
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Given:
1. class Eco {
2. public static void main(String[] args) {
3. Eco e1 = new Eco();
4. Eco e2 = new Eco();
5. Eco e3 = new Eco();
6. e3.e = e2;
7. e1.e = e3;
8. e2 = null;
9. e3 = null;
10. e2.e = e1;
11. e1 = null;
12. }
13. Eco e;
14. }
At what point is only a single object eligible for GC?


A. After line 8 runs.
B. After line 9 runs.
C. After line 10 runs.
D. After line 11 runs.
E. Compilation fails.
F. Never in this program.
G. An exception is thrown at runtime.
Answer:
� 3 G is correct. An error at line 10 causes a NullPointerException to be thrown because
e2 was set to null in line 8. If line 10 was moved between lines 7 and 8, then F would be
correct, because until the last reference is nulled none of the objects is eligible, and once
the last reference is nulled, all three are eligible.
�˚ A, B, C, D, E, and F are incorrect based on the above.
 
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