code: public static byte[][] copyOf(final byte[][] a, final int s) {
          final byte[][] tmp = new byte[s][];
          System.arraycopy(a, 0, tmp, 0, Math.min(s, a.length));
          return tmp;
      }
docs: Copies the specified array.
  
  @param a array to be copied
  @param s new array size
  @return new array