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7. Garbage Collections
Q: 01 Given: 1. public class GC { 2. private Object o; 3. private void doSomethingElse(Object obj) { o = obj; } 4. public void doSomething() { 5. Object o = new Object(); 6. doSomethingElse(o); 7. o = new Object(); 8. doSomethingElse(null); 9. o = null; 10. } 11. } When the doSomething method is called, after which line does the Object created in line 5 become available for garbage collection? A. Line 5 B. Line 6 C. Line 7 D. Line 8 E. Line 9 F. Line 10 Answer: D Q: 02 Given: 11. public void genNumbers() { 12. ArrayList numbers = new ArrayList(); 13. for (int i=0; i<10; i++) { 14. int value = i * ((int) Math.random()); 15. Integer intObj = new Integer(value); 16. numbers.add(intObj); 17. } 18. System.out.println(numbers); 19. } Which line of code marks the earliest point that an object referenced by intObj becomes a candidate for garbage collection? A. Line 16 B. Line 17 C. Line 18 D. Line 19 E. The object is NOT a candidate for garbage collection. Answer: D Q: 03 Given: 11. rbo = new ReallyBigObject(); 12. // more code here 13. rbo = null; 14. /* insert code here */ Which statement should be placed at line 14 to suggest that the virtual machine expend effort toward recycling the memory used by the object rbo? A. System.gc(); B. Runtime.gc(); C. System.freeMemory(); D. Runtime.getRuntime().growHeap(); E. Runtime.getRuntime().freeMemory(); Answer: A
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