/**
* Adds the specified element to this set if it is not already present and the element >= 0.
*
* @param e element to be added to this set
* @return <tt>true</tt> if this set did not already contain the specified element and the element
* >= 0
*/
@Override
public boolean add(Integer e) {
if (e < 0) throw new RuntimeException("To add a negative number: " + e);
if (contains(e)) {
return false;
}
int wordIndex = wordIndex(e);
expandTo(wordIndex);
words[wordIndex] |= (1L << e);
++size;
++modCount;
return true;
}
