For definition of "check point" see IndexWriter comments: "Clarification: Check Points (and commits)". Writer calls this when it has made a "consistent change" to the index, meaning new files are written to the index and the in-memory SegmentInfos have been modified to point to those files. This may or may not be a commit (segments_N may or may not have been written). We simply incref the files referenced by the new SegmentInfos and decref the files we had previously seen (if any). If this is a commit, we also call the policy to give it a chance to remove other commits. If any commits are removed, we decref their files as well.

Determines whether the specified Object is equal to the current Object.

Allows an Object to attempt to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection.

Serves as a hash function for a particular type.

Gets the Type of the current instance.

Creates a shallow copy of the current Object.

Writer calls this when it has hit an error and had to roll back, to tell us that there may now be unreferenced files in the filesystem. So we re-list the filesystem and delete such files. If segmentName is non-null, we will only delete files corresponding to that segment.

Returns a String that represents the current Object.