How to find out opened readers in Lucene

[andi rexha]

Hi, 
I have some IndexReaders and a single IndexWriter opened. I index some 
documents, and in the end only one reader should be opened and the old 
ones should be closed. The readers should be closed, but when I restart 
the system(meaning I restart the IndexWriter), actually the size of the 
index in disk shrinks at least by half, meaning that probably some 
readers were still opened. Is there any way to figure out the readers 
per commit that are still in use in a certain moment?