— Scott McNealy, Sun Microsystems Chairman, President and ceo

API
558
 
chapter 16
HashSet
Set
extends
implements
implementation class
interface
KEY
Collection
(interface)
Set
(interface)
List
(interface)
SortedSet
(interface)
Map
(interface)
SortedMap
(interface)
 LinkedList
Vector
 TreeSet
 LinkedHashSet
 HashSet
 ArrayList
 TreeMap
 Hashtable
 LinkedHashMap
 HashMap
The Collection API (part of it)
Notice that the Map interface doesn’t 
actually extend the Collection interface, 
but Map is still considered part of the 
“Collection Framework” (also known 
as the “Collection API”). So Maps are 
still collections, even though they don’t 
include java.util.Collection in their 
inheritance tree.
(Note: this is not the complete
collection API; there are other
classes and interfaces, but 
these are the ones we care
most about.)
Maps don’t extend from 
java.util.Collection, but 
they’re still considered 
to be part of the 
“collections framework” 
in Java. So a Map is 
still referred to as a 
collection.

---

collections 
with 
generics
you are here
4
559
We added on to the Jukebox to put the songs in a HashSet. (Note: we left out some 
of the Jukebox code, but you can copy it from earlier versions. And to make it easier 
to read the output, we went back to the earlier version of the Song’s toString() 
method, so that it prints only the title instead of title and artist.)
Using a HashSet instead of ArrayList
import java.util.*;
import java.io.*;
public class Jukebox6 { 
ArrayList songList = new ArrayList(); 
// main method etc.
public void go() { 
getSongs(); 
System.out.println(songList);
Collections.sort(songList);
System.out.println(songList);