public static byte[] concat(final byte[] first,final int lenFirst,final byte[] second,final int lenSecond){
  final byte[] sum=new byte[lenFirst + lenSecond];
  System.arraycopy(first,0,sum,0,lenFirst);
  System.arraycopy(second,0,sum,lenFirst,lenSecond);
  return sum;
}

public static byte [ ] concat ( final byte [ ] first , final int lenFirst , final byte [ ] second , final int lenSecond ) { final byte [ ] sum = new byte [ lenFirst + lenSecond ] ; System . arraycopy ( first , 0 , sum , 0 , lenFirst ) ; System . arraycopy ( second , 0 , sum , lenFirst , lenSecond ) ; return sum ; }
concatena first e second .
