/**
* Removes e from the set, and throws an IllegalArgumentException if e is null
*
* @param e
*/
public void remove(String e) {
if (e == null) throw new IllegalArgumentException();
for (int i = 0; i < data.size(); i++) {
if (data.get(i).equals(e)) {
data.remove(i);
break;
}
}
}
