public Set < K > getUnmatchedKeys ( ) { stateLock . readLock ( ) . lock ( ) ; try { return new HashSet < K > ( this . actualIndices . keySet ( ) ) ; } finally { stateLock . readLock ( ) . unlock ( ) ; } }
Get a point - in - time view of the unmatched keys . This may be immediately out of date unless additional synchronization is performed to prevent concurrent updates .