If you only have one tag then this issue does not occur, but more than one tag in a single note leads to a crash.
Steps to reproduce:
Add a new note with more than one tag, for example "#this #crashes"
Save the note
Delete the note
Logcat output:
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.next(ArrayList.java:860)
at com.notes.sum.sec.TagManager.addTags(TagManager.java:33)
at com.notes.sum.sec.TagManager.removeTags(TagManager.java:88)
at com.notes.sum.sec.NoteManager.removeNote(NoteManager.java:94)
at com.notes.sum.ActivityMain$6.onClick(ActivityMain.java:219)
If you only have one tag then this issue does not occur, but more than one tag in a single note leads to a crash.
Steps to reproduce:
Logcat output: