The collections api - Data Structures and Problem Solving Using Java - page 263

1 package weiss.util;
2
3 /**
4 * SortedSet interface.
5 */
6 public interface SortedSet<AnyType> extends Set<AnyType>
7 {
8 /**
9 * Return the comparator used by this SortedSet.
10 * @return the comparator or null if the
11 * default comparator is used.
12 */
13 Comparator<? super AnyType> comparator( );
14
15 /**
16 * Find the smallest item in the set.
17 * @return the smallest item.
18 * @throws NoSuchElementException if the set is empty.
19 */
20 AnyType first( );
21
22 /**
23 * Find the largest item in the set.
24 * @return the largest item.
25 * @throws NoSuchElementException if the set is empty.
26 */
27

figure 6.30
Possible SortedSet
interface

AnyType last( );

28 }

A SortedSet is a Set that maintains (internally) its items in sorted order.
Objects that are added into the SortedSet must either be comparable, or a
Comparator has to be provided when the container is instantiated. A SortedSet
supports all of the Set methods, but its iterator is guaranteed to step through
items in its sorted order. The SortedSet also allows us to find the smallest
and largest item. The interface for our subset of SortedSet is shown in
Figure 6.30.

The SortedSet is an
ordered container.
It allows no
duplicates.

6.7.1 the TreeSet class

The SortedSet is implemented by a TreeSet . The underlying implementation
of the TreeSet is a balanced-binary search tree and is discussed in Chapter 19.
By default, ordering uses the default comparator. An alternate ordering
can be specified by providing a comparator to the constructor. As an example,
Figure 6.31 illustrates how a SortedSet that stores strings is constructed. The
call to printCollection will output elements in decreasing sorted order.
The SortedSet , like all Set s, does not allow duplicates. Two items are con-
sidered equal if the comparator's compare method returns 0.

The TreeSet is an
implementation of
SortedSet .