question: public static byte [ ] concatenate ( byte [ ] a , byte [ ] b ) { byte [ ] output = new byte [ a . length + b . length ] ; System . arraycopy ( a , 0 , output , 0 , a . length ) ; System . arraycopy ( b , 0 , output , a . length , b . length ) ; return output ; }
target:  Concatenates two byte arrays.