public T get ( long seqno ) { lock . lock ( ) ; try { if ( seqno - low <= 0 || seqno - hr > 0 ) return null ; int row_index = computeRow ( seqno ) ; if ( row_index < 0 || row_index >= matrix . length ) return null ; T [ ] row = matrix [ row_index ] ; if ( row == null ) return null ; int index = computeIndex ( seqno ) ; return index >= 0 ? row [ index ] : null ; } finally { lock . unlock ( ) ; } }
Returns an element at seqno