SETS AND MAPS - Introduction to Java Programming: Comprehensive Version - page 799

«interface»
java.util.Collection < E >

«interface»
java.util.Set < E >

java.util.AbstractSet < E >

«interface»
java.util.SortedSet<E>

+ first(): E
+ last(): E
+ headSet(toElement: E): SortedSet < E >
+ tailSet(fromElement: E): SortedSet < E >

java.util.HashSet<E>

+HashSet()
+HashSet(c: Collection<? extends E>)
+HashSet(initialCapacity: int)
+HashSet(initialCapacity: int, loadFactor: float)

«interface»
java.util.NavigableSet<E>

java.util.LinkedHashSet<E>

+ pollFirst(): E
+ pollLast(): E
+ lower(e: E): E
+ higher(e: E):E
+ floor(e: E): E
+ ceiling(e: E): E

+LinkedHashSet()
+LinkedHashSet(c: Collection<? extends E>)
+LinkedHashSet(initialCapacity: int)
+LinkedHashSet(initialCapacity: int, loadFactor: float)

java.util.TreeSet<E>

+TreeSet()
+TreeSet(c: Collection<? extends E>)
+TreeSet(comparator: Comparator<?
super E>)
+TreeSet(s: SortedSet<E>)

F IGURE 21.1

The Java Collections Framework provides three concrete set classes.

Listing 21.1 gives a program that creates a hash set to store strings and uses a foreach loop
to traverse the elements in the set.

L ISTING 21.1

TestHashSet.java
1 import java.util.*;
2
3 public class TestHashSet {
4

public static void main(String[] args) {

5 // Create a hash set

6 Set<String> set = new HashSet<>();

create a set

7
8 // Add strings to the set
9 set.add( "London" );
10 set.add( "Paris" );
11 set.add( "New York" );
12 set.add( "San Francisco" );
13 set.add( "Beijing" );

add element