code: public void addFalsePositive(Key key) {
      if (key == null) {
        throw new NullPointerException("key can not be null");
      }
  
      int[] h = hash.hash(key);
      hash.clear();
  
      for (int i = 0; i < nbHash; i++) {
        fpVector[h[i]].add(key);
      }
    }
docs: Adds a false positive information to <i>this</i> retouched Bloom filter.
  <p>
  <b>Invariant</b>: if the false positive is <code>null</code>, nothing happens.
  @param key The false positive key to add.