Java: Set interface and Collection interface differences

I just looked up the Set interface and found that it mostly (or completely) only redeclares functions which are already in the Collection interface. Set itself extends Collection, so doesn't that mean that the Set interface automatically has all the functions from Collection? So why are they redeclared then?

For example, Set redeclares this:

/**
 * Returns the number of elements in this set (its cardinality).  If this
 * set contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
 * <tt>Integer.MAX_VALUE</tt>.
 *
 * @return the number of elements in this set (its cardinality)
 */
int size();

/**
 * Returns <tt>true</tt> if this set contains no elements.
 *
 * @return <tt>true</tt> if this set contains no elements
 */
boolean isEmpty();

And the declaration in Collection:

/**
 * Returns the number of elements in this collection.  If this collection
 * contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
 * <tt>Integer.MAX_VALUE</tt>.
 *
 * @return the number of elements in this collection
 */
int size();

/**
 * Returns <tt>true</tt> if this collection contains no elements.
 *
 * @return <tt>true</tt> if this collection contains no elements
 */
boolean isEmpty();

This seems very redundant to me. Why not just define the Set interface as:

public interface Set<E> extends Collection<E> {}

I think there is no single difference between those interfaces, right?

Of course I am not asking about the different semantics / meaning of Set. I know that. I am just asking about if it technically (i.e. to the compiler) has any difference. I.e., speaking generally:

interface A { void foo(); }