question: static byte [ ] joinDataAndKnown ( final byte [ ] data ) { final byte [ ] dataAndCheck = new byte [ KNOWN_VAL . length + data . length ] ; System . arraycopy ( KNOWN_VAL , 0 , dataAndCheck , 0 , KNOWN_VAL . length ) ; System . arraycopy ( data , 0 , dataAndCheck , KNOWN_VAL . length , data . length ) ; return dataAndCheck ; }
target:  Join known and data into one array. <p> package access so we can test.