Proble with synchronization

Question

I hvae seen some where the follwing question
Given:
public class NamedCounter {
private final String name;
private int count;
public NamedCounter(String name) { this.name = name; }
public String getName() { return name; }
public void increment() { coount++; }
public int getCount() { return count; }
public void reset() { count = 0; }
Which three changes should be made to adapt this class to be used
safely by multiple threads? (Choose three.)
A. declare reset() using the synchronized keyword
B. declare getName() using the synchronized keyword
C. declare getCount() using the synchronized keyword
D. declare the constructor using the synchronized keyword
E. declare increment() using the synchronized keyword
ANS :-   ACE
Problem :- I have a doubt with the oprion c, it simply returns the value of count then why synchronized the getCount() function, mostly we synchronized the function which changes the value of variable.
Edited by: rahul_p on Jun 4, 2008 10:51 PM

Answer 1

rahul_p wrote:
Problem :- I have a doubt with the oprion c, it simply returns the value of count then why synchronized the getCount() function, mostly we synchronized the function which changes the value of variable.In terms of concurrency and getting a valid value, no syncing is needed on the getter. (This would not be true if it were a long.)
However, even though it's "safe", in that the getter cannot read corrupt data, it can read stale data. Since each thread is allowed to keep a local copy of shared variables, it's entirely possible that after one thread writes a new value to count, no other thread will ever read that value. Entry to and exit from a sync block or method forces a reconciliation between the thread's local copy and the main copy.