question: public static byte [ ] concatenate ( byte [ ] x1 , byte [ ] x2 ) { byte [ ] result = new byte [ x1 . length + x2 . length ] ; System . arraycopy ( x1 , 0 , result , 0 , x1 . length ) ; System . arraycopy ( x2 , 0 , result , x1 . length , x2 . length ) ; return result ; }
target:  Concatenate two byte arrays. No null checks are performed.