Hey Toni. Yes, I verified that this is the exact spot where the NPE occurs. More than 10 times ;) It would be possible though that the tag I used wasn't accurate, but even then I wouldn't know which of the variables could be null and fail in that way. The databaseHelper is also initialized in the constructor.
No, I didn't leave out the synchronization, but I think it wouldn't make any difference as this would "only" affect if an item is in the Map, not if the Map is instantiated/null. This should be concluded after the constructor is left and the object is kicked into life, right? Just because I am so unsure, I tried to call Map.get as well as Map.put with null and interestingly enough it works. If I put some Object with a key of null into the Map I get the same object back when I access the Map again with null as the key. But that is actually not really relevant here – I think – as the NPE happens right on the last line and not inside the Map implementation, which would be the case if the Map would have an issue with a null. Thanks for helping me to think here ;) Cheers, Mariano On Tue, Jun 22, 2010 at 12:08 PM, Toni Menzel <[email protected]> wrote: > Hi Mariano, > > First of all, did you leave out synchronization for simplicity in this > mail or is it not in place at all ? > (assuming you do access EntityManager from multiple threads). > > Also, pls doublecheck that EntryManager.java:1529 is really at the > spot you indicated (cannot verify with complete sources). > Specifically i am unsure about databaseHelper. Its just accessed in > you example, so could be null. > > At best give the full file so we can check. > > Toni > > On Tue, Jun 22, 2010 at 11:59 AM, Mariano Kamp <[email protected]> > wrote: > > Hey guys. > > This is not an Android issue per-se, but I am puzzled about a Java issue > and > > want to pick your brains. > > I recently got a couple of bug reports with a NPE that I don't understand > > and can't reproduce myself. Here is an abbreviated representation of the > > offending class. I tried to stay as close to the actual code as possible. > > public class EntryManager { > > private static EntryManager instance; > > private Map<DBQuery, Boolean> isMarkAllReadPossibleCache; > > private EntryManager(Context ctx) { > > .. > > isMarkAllReadPossibleCache = new HashMap<DBQuery, Boolean>(); > > databaseHelper = new DB(ctx); > > .. > } > > public static synchronized EntryManager getInstance(final Context > context) > > { > > if (instance == null) > > instance = new EntryManager(context.getApplicationContext()); > > return instance; > > } > > void fireModelUpdated(final String atomId) { > > .. > > isMarkAllReadPossibleCache.clear(); > > .. > > } > > public boolean isMarkAllReadPossible(final DBQuery dbq) { > > if (!isMarkAllReadPossibleCache.containsKey(dbq)) > > isMarkAllReadPossibleCache.put(dbq, > > databaseHelper.isMarkAllReadPossible(dbq)); > > return isMarkAllReadPossibleCache.get(dbq); <!-- NPE is raised > here > > } > > .. > > } > > In the last line from above a NPE is thrown. So the instance variable > > isMarkAllReadPossibleCache must be null, right? But I don't see where > this > > could happen. It's initialized in the constructor and never set to null > > afterwards. > > For completeness here is a stack trace: > > > > java.lang.NullPointerException > > at com.newsrob.EntryManager.isMarkAllReadPossible(EntryManager.java:1529) > > at > > > com.newsrob.activities.AbstractNewsRobListActivity.shouldMarkAllReadButtonBeEnabled(AbstractNewsRobListActivity.java:327) > > at > > > com.newsrob.activities.AbstractNewsRobListActivity.updateButtons(AbstractNewsRobListActivity.java:236) > > at > > > com.newsrob.activities.AbstractNewsRobListActivity.access$2(AbstractNewsRobListActivity.java:215) > > <-- removed the private access modifier meanwhile > > at > > > com.newsrob.activities.AbstractNewsRobListActivity$13.run(AbstractNewsRobListActivity.java:626) > > at android.os.Handler.handleCallback(Handler.java:587) > > at android.os.Handler.dispatchMessage(Handler.java:92) > > at android.os.Looper.loop(Looper.java:123) > > at android.app.ActivityThread.main(ActivityThread.java:4203) > > at java.lang.reflect.Method.invokeNative(Native Method) > > at java.lang.reflect.Method.invoke(Method.java:521) > > at > > > com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) > > at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549) > > at dalvik.system.NativeStart.main(Native Method) > > Any ideas? > > Cheers, > > Mariano > > > > -- > > 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]<android-developers%[email protected]> > > For more options, visit this group at > > http://groups.google.com/group/android-developers?hl=en > > > > -- > Toni Menzel > Independent Software Developer > Professional Profile: http://okidokiteam.com > [email protected] > http://www.ops4j.org - New Energy for OSS Communities - Open > Participation Software. > > -- > 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]<android-developers%[email protected]> > For more options, visit this group at > http://groups.google.com/group/android-developers?hl=en -- You received this message because you are subscribed to the Google Groups "Android Developers" group. 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