NumberFormatException: For input string: "gen.before_restore_2011-03-21_07.15.36.372112" [LUCENE-3008]

Hello,

One of our users reported the following stacktrace:

Exception in thread "Thread-3" java.lang.NumberFormatException: For input string: "gen.before_restore_2011-03-21_07.15.36.372112"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Long.parseLong(Long.java:419)
at org.apache.lucene.index.SegmentInfos.generationFromSegmentsFileName(SegmentInfos.java:199)
at org.apache.lucene.index.SegmentInfos.getCurrentSegmentGeneration(SegmentInfos.java:134)
at org.apache.lucene.index.SegmentInfos.getCurrentSegmentGeneration(SegmentInfos.java:151)
at org.apache.lucene.index.IndexReader.indexExists(IndexReader.java:626)
at org.apache.lucene.index.IndexWriter.init(IndexWriter.java:1015)
at org.apache.lucene.index.IndexWriter.<init>(IndexWriter.java:887)
at net.sourceforge.docfetcher.model.RootScope.updateIndex(RootScope.java:138)
at net.sourceforge.docfetcher.model.ScopeRegistry$2.run(ScopeRegistry.java:392)

I'm afraid I can't provide any more information than this, other than the Lucene version: 3.0.0

Best regards
Tran Nam Quang

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Migrated from [LUCENE-3008](https://issues.apache.org/jira/browse/LUCENE-3008) by Nam-Quang Tran, updated Apr 20 2011

Start with SegmentInfos.generationFromSegmentsFileName and getCurrentSegmentGeneration, which appear in the stack trace, then trace the call through IndexReader.indexExists and IndexWriter.init. The report provides no reproduction beyond the stack trace and Lucene 3.0.0, so first determine how this filename reaches the generation parser. Done means the cause is reproducible and the handling is covered by an appropriate regression test.

Written by the indexing model from the issue text.