android/guava/src/com/google/common/collect/ForwardingNavigableSet.java
protected E standardFloor(E e) {
    return Iterators.getNext(headSet(e, true).descendingIterator(), null);
  }
protected E standardFloor(E e) {
    return Iterators.getNext(headSet(e, true).descendingIterator(), null);
  }
protected E standardFloor ( E e ) { return Iterators . getNext ( headSet ( e , true ) . descendingIterator ( ) , null ) ; }
A sensible definition of {@link #floor} in terms of the {@code descendingIterator} method of
{@link #headSet(Object, boolean)}. If you override {@link #headSet(Object, boolean)}, you may
wish to override {@link #floor} to forward to this implementation.
A sensible definition of {