@Override
    public void apply(byte[] val) {
      for (int i = 0; i < val.length; i++) {
        val[i] ^= MASK;
      }
    }
A {@code byte} value is inverted by taking its 1's Complement, achieved via {@code xor} with
{@code 0xff}.
hbase-common/src/main/java/org/apache/hadoop/hbase/util/Order.java