docs: public boolean add(final int value) {
          if (size == capacity) {
              throw new IllegalStateException("This IntHashSet of capacity " + capacity + " is full");
          }
          int index = intHash(value, mask);
  
          while (values[index] != missingValue) {
              if (values[index] == value) {
                  return false;
              }
  
              index = next(index);
          }
  
          values[index] = value;
          size++;
  
          return true;
      }