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Java Forum / Virtual Machine / September 2007Synchronized implementations
I have noticed a few times that Java implements synchronized blocks thusly: aload 4 dup astore 5 monitorenter [ various instructions ] aload 5 monitorexit Why does it duplicate the variable when running synchronized blocks?  SignatureBeware of bugs in the above code; I have only proved it correct, not tried it. -- Donald E. Knuth On Thu, 13 Sep 2007 01:27:03 GMT, Joshua Cranmer <Pidgeot18@verizon.net> wrote, quoted or indirectly quoted someone who said : >astore 5 >monitorenter [quoted text clipped - 3 lines] > >Why does it duplicate the variable when running synchronized blocks? Byte code has almost no optimisation. Sun does all its optimisations in HotSpot. SignatureRoedy Green Canadian Mind Products The Java Glossary http://mindprod.com > I have noticed a few times that Java implements synchronized blocks thusly: > [quoted text clipped - 7 lines] > > Why does it duplicate the variable when running synchronized blocks? Because you might have code like this: synchronized (something) { ... something := somethingElse; ... } Signature--------------------------- | BBB b \ Barbara at LivingHistory stop co stop uk | B B aa rrr b | | BBB a a r bbb | Quidquid latine dictum sit, | B B a a r b b | altum viditur. | BBB aa a r bbb | ----------------------------- Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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