Returns a view of the portion of this set whose elements are strictly less than
toElement. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports.
The returned set will throw an IllegalArgumentException on an attempt to insert an element outside its range.
@param toElement high endpoint (exclusive) of the returned set
@return a view of the portion of this set whose elements are strictlyless than toElement
@throws ClassCastException if toElement is not compatiblewith this set's comparator (or, if the set has no comparator, if toElement does not implement {@link Comparable}). Implementations may, but are not required to, throw this exception if toElement cannot be compared to elements currently in the set.
@throws NullPointerException if toElement is null andthis set does not permit null elements
@throws IllegalArgumentException if this set itself has arestricted range, and toElement lies outside the bounds of the range