java.util.ConcurrentModificationException and SharedPreference

Question

I've found this crash in crash logs. I don't know when it is happening. Can someone give me advice what is the reason? Maybe someone has same crash.

java.util.ConcurrentModificationException
       at java.util.HashMap$HashIterator.nextEntry(HashMap.java:787)
       at java.util.HashMap$KeyIterator.next(HashMap.java:814)
       at com.android.internal.util.XmlUtils.writeSetXml(XmlUtils.java:350)
       at com.android.internal.util.XmlUtils.writeValueXml(XmlUtils.java:688)
       at com.android.internal.util.XmlUtils.writeMapXml(XmlUtils.java:295)
       at com.android.internal.util.XmlUtils.writeMapXml(XmlUtils.java:264)
       at com.android.internal.util.XmlUtils.writeMapXml(XmlUtils.java:230)
       at com.android.internal.util.XmlUtils.writeMapXml(XmlUtils.java:187)
       at android.app.SharedPreferencesImpl.writeToFile(SharedPreferencesImpl.java:597)
       at android.app.SharedPreferencesImpl.access$800(SharedPreferencesImpl.java:51)
       at android.app.SharedPreferencesImpl$2.run(SharedPreferencesImpl.java:512)
       at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
       at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
       at java.lang.Thread.run(Thread.java:818)

Answer 1

We had seen this exception when using the SharedPreferences getStringSet method. This method returns a set that should not be modified. Modifying this set while the SharedPreferences object is being serialized to flash will produce a ConcurrentModificationException.

This will also happen if you use getAll and modify the returned map.

See the documentation