Lucene encourages the reuse of an IndexWriter from multiple threads.
Given that two threads might have a reference to the IndexWriter, if thread A calls close on the writer, thread B would be left with a useless writer. But to my understanding lucene somehow knows that another thread uses the same writer and defers its closure.
Is this indeed the case? How does lucene track that another thread uses the writer?
EDIT Judging from the answers it is not correct to close the IndexWriter. But this poses a new issue: If one keeps an IndexWriter open, essentially blocks access to this index from another JVM (eg in case of a cluster, or a shared index between many applications).