question: private byte [ ] concat ( final byte [ ] data1 , final byte [ ] data2 ) { final byte [ ] newdata = new byte [ data1 . length + data2 . length ] ; System . arraycopy ( data1 , 0 , newdata , 0 , data1 . length ) ; System . arraycopy ( data2 , 0 , newdata , data1 . length , data2 . length ) ; return newdata ; }
target:  Concatenates two byte arrays.