Closing Android databases across Parallel Threads

I am asking this question in context of a problem in my app, about which I find it difficult to create an exact question. But I do have a lead.

I do have parallel threads running and my problem revolves around the case where running queries on database returns NullpointerException on the initialized database instance.

So what I want to know is that if you initialize an instance of a database by db.getWritableDatabase() in 2 parallel threads, does closing the database in one thread by db.close(), closes it in the other thread ? infact across the application level ?