java.nio.channels.ClosedChannelException
   at sun.nio.ch.FileChannelImpl.ensureOpen(FileChannelImpl.java:88)
   at sun.nio.ch.FileChannelImpl.read(FileChannelImpl.java:613)
   at org.apache.lucene.store.NIOFSDirectory$NIOFSIndexInput.readInternal(NIOFSDirectory.java:168)
   at org.apache.lucene.store.BufferedIndexInput.refill(BufferedIndexInput.java:160)
   at org.apache.lucene.store.BufferedIndexInput.readByte(BufferedIndexInput.java:39)
   at org.apache.lucene.store.IndexInput.readVInt(IndexInput.java:79)
   at org.apache.lucene.index.TermBuffer.read(TermBuffer.java:64)
   at org.apache.lucene.index.SegmentTermEnum.next(SegmentTermEnum.java:131)
   at org.apache.lucene.index.SegmentTermEnum.scanTo(SegmentTermEnum.java:162)
   at org.apache.lucene.index.TermInfosReader.get(TermInfosReader.java:232)
   at org.apache.lucene.index.TermInfosReader.get(TermInfosReader.java:179)
   at org.apache.lucene.index.SegmentReader.docFreq(SegmentReader.java:975)
   at org.apache.lucene.index.DirectoryReader.docFreq(DirectoryReader.java:659)
   at org.apache.lucene.search.IndexSearcher.docFreq(IndexSearcher.java:138)
   at org.apache.lucene.search.Similarity.idfExplain(Similarity.java:735)
   at org.apache.lucene.search.TermQuery$TermWeight.<init>(TermQuery.java:46)
   at org.apache.lucene.search.TermQuery.createWeight(TermQuery.java:171)
   at org.apache.lucene.search.Query.weight(Query.java:101)
   at org.apache.lucene.search.Searcher.createWeight(Searcher.java:147)
   at org.apache.lucene.search.Searcher.search(Searcher.java:67)
   at org.apache.maven.index.context.DefaultIndexingContext.getGroups(DefaultIndexingContext.java:1090)
   at org.apache.maven.index.context.DefaultIndexingContext.getAllGroups(DefaultIndexingContext.java:1028)
   at org.netbeans.modules.maven.indexer.NexusRepositoryIndexerImpl$6.run(NexusRepositoryIndexerImpl.java:743)
   at org.netbeans.modules.maven.indexer.NexusRepositoryIndexerImpl$6.run(NexusRepositoryIndexerImpl.java:733)
Caused: org.openide.util.MutexException: java.nio.channels.ClosedChannelException
   at org.openide.util.Mutex.writeAccess(Mutex.java:440)
   at org.netbeans.modules.maven.indexer.NexusRepositoryIndexerImpl.filterGroupIds(NexusRepositoryIndexerImpl.java:733)
   at org.netbeans.modules.maven.indexer.NexusRepositoryIndexerImpl.getGroups(NexusRepositoryIndexerImpl.java:724)
   at org.netbeans.modules.maven.indexer.api.RepositoryQueries.getGroups(RepositoryQueries.java:85)
   at org.netbeans.modules.maven.repository.GroupListChildren.createKeys(GroupListChildren.java:77)
   at org.openide.nodes.AsynchChildren.run(AsynchChildren.java:189)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1424)
   at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1968)