bob wrote: > > Yes, it's thread-safe because setting a boolean is an atomic operation. > That is fallacious.
Setting a boolean may be atomic, but that has nothing to do with thread safety. Thread safety in Java is determined by "happens-before" relationships and related concepts. http://docs.oracle.com/javase/specs/jls/se7/html/jls-17.html#jls-17.4 specifically http://docs.oracle.com/javase/specs/jls/se7/html/jls-17.html#jls-17.4.5 Please do not promulgate false information. sdb wrote: > > I'm new to android development and have been studying the Lunar Lander > example included in the SDK to get a better understanding of how the > SurfaceView works. I noticed that the mRun member of the LunarThread class > is updated by the setRunnable() method of the LunarThread class which is > called from the LunarView class within the surfaceCreated() and > surfaceDestroyed() methods. Per the referenced link, you can see that 'thread.start()' is a synchronization edge. So the use in 'surfaceCreated()' is thread safe. However, the synchronization edge for 'join()' is after it returns , which to my eye means that 'surfaceDestroyed()' is not. > It seems to me that mRun is being updated by the main thread for the SurfaceView, > but is being repeatedly read in a tight loop in LunarThread. My question is: is this > use of mRun thread safe and if so, why/how? >I'm not sure, but maybe it is thread safe because mRun is a simple boolean variable Nope. Being a "simple boolean variable" doesn't make it thread safe. > and is only updated from one of the two threads involved. If mRun was a more complext Nope. Being *accessed* is what counts, not just updated. > object and/or it was being updated by different by both threads,then perhaps this example > would not be thread safe without the use of some form of synchronization mechanism. As it likely isn't now, unless my analysis is incorrect. -- Lew -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
