question: final public static String toString ( final byte [ ] key , final int off , final int len ) { if ( key == null ) return NULL ; final StringBuilder sb = new StringBuilder ( len * 4 + 2 ) ; sb . append ( "[" ) ; for ( int i = off ; i < off + len ; i ++ ) { if ( i > 0 ) sb . append ( "," ) ; sb . append ( Integer . toString ( key [ i ] & 0xff ) ) ; } sb . append ( "]" ) ; return sb . toString ( ) ; }
target:  Formats a key as a series of comma delimited unsigned bytes.