android/guava/src/com/google/common/collect/ForwardingNavigableSet.java
@Override
  protected SortedSet<E> standardSubSet(E fromElement, E toElement) {
    return subSet(fromElement, true, toElement, false);
  }
@Override
  protected SortedSet<E> standardSubSet(E fromElement, E toElement) {
    return subSet(fromElement, true, toElement, false);
  }
A sensible definition of {@link #subSet(Object, Object)} in terms of the {@link #subSet(Object,
boolean, Object, boolean)} method. If you override {@link #subSet(Object, boolean, Object,
boolean)}, you may wish to override {@link #subSet(Object, Object)} to forward to this
implementation.