Re: switch using strings
On 3/2/2011 10:42 PM, javax.swing.JSnarker wrote:
On 02/03/2011 10:34 PM, Eric Sosman wrote:
Agreed. For example, choosing not to have autoboxing.
Well, it looks like the problem is that the lock isn't on a consistent
object. Of course, making the whole method synchronized fixes it if
there are no other synchronized methods in the class, or other things
synching on its instances.
Bingo! Well, the phraseology is a little strange: Since the lock
is on one object, period, it's on a "consistent object." However, there
are two objects in play (three, counting the Paraphrase instance), and
the locked object turns out not to be the right one.
Ultimately, the problem lies with autoboxing using the immutable
Integer, etc. classes and not mutable versions of these, or else with
the way locking itself works. It probably couldn't easily be fixed in a
backwards-compatible way, unfortunately.
Pre-1.5, the programmer would have written
private Integer count = Integer.valueOf(0);
void increment() {
synchronized(count) {
count = Integer.valueOf(count.intValue() + 1);
.... and right about here would quite likely have said "Oh, wait..."
That's why I believe autoboxing contributed to the bug.
I must wonder why whoever wrote that code didn't just use AtomicInteger...
.... for which there's no autoboxing. The prosecution rests.
--
Eric Sosman
esosman@ieee-dot-org.invalid