import java.util.*; D:\java SetDemo3 public class SetDemo3{ string1 add returns true public static void main(String args[]){ string2 add returns true boolean b; string3 add returns true Set s new HashSet(); string1 add returns false b =s.add("string1"); string2 add returns false System.out.println("string1 add returns"+b);string3 b s.add("string2"); string1 System.out.println("string2 add returns"+b); string2 b s.add("string3"); System.out.println("string3 add returns"+b); D b s.add("string1"); System.out.println("string1 add returns"+b); b s.add("string2"); java.util.Iterator System.out.println("string2 add returns"+b); 迭代器(interface) Iterator i s.iterator(); ·轮循 while (i.hasNext()) System.out.println(i.next(); 无序输出 11
11 ◼ HashSet(无序集合) 对象集合(Set) import java.util.*; public class SetDemo3 { public static void main(String args[]) { boolean b; Set s = new HashSet(); b = s.add("string1"); System.out.println("string1 add returns " + b); b = s.add("string2"); System.out.println("string2 add returns " + b); b = s.add("string3"); System.out.println("string3 add returns " + b); b = s.add("string1"); System.out.println("string1 add returns " + b); b = s.add("string2"); System.out.println("string2 add returns " + b); Iterator i = s.iterator(); while (i.hasNext()) System.out.println(i.next()); } } D:\java SetDemo3 string1 add returns true string2 add returns true string3 add returns true string1 add returns false string2 add returns false string3 string1 string2 D:\ java.util.Iterator 迭代器(interface) •轮循 无序输出
HashSet:Set implemented via a hash table TreeSet:SortedSet implemented as a tree java.util.Set (interface) java.util.HashSet java.util.SortedSet (class) (interface) 无序集合 ijava.util.TreeSet (class) 有序集合 12
12 对象集合(Set) java.util.Set (interface) java.util.SortedSet (interface) java.util.HashSet (class) java.util.TreeSet (class) 无序集合 有序集合 HashSet: Set implemented via a hash table TreeSet: SortedSet implemented as a tree
import java.util.*; D:\java SetDemo4 public class SetDemo4{ string1 add returns true public static void main(String args[]){ string2 add returns true boolean b; string3 add returns true Set s new TreeSet(); string1 add returns false b s.add("string1"); string2 add returns false System.out.println("string1 add returns"+b);string1 b s.add("string2"); string2 System.out.printin("string2 add returns "b);surings b s.add("string3"); System.out.println("string3 add returns"+b); D b =s.add("string1"); System.out.println("string1 add returns"+b); b s.add("string2"); java.util.Iterator System.out.println("string2 add returns"+b); 迭代器(interface) Iterator i s.iterator(); ·轮循 while (i.hasNext()) System.out.println(i.next(); 有序输出（自然顺序） 13
13 ◼ java.util.TreeSet implement java.util.SortedSet 对象集合(Set) import java.util.*; public class SetDemo4 { public static void main(String args[]) { boolean b; Set s = new TreeSet(); b = s.add("string1"); System.out.println("string1 add returns " + b); b = s.add("string2"); System.out.println("string2 add returns " + b); b = s.add("string3"); System.out.println("string3 add returns " + b); b = s.add("string1"); System.out.println("string1 add returns " + b); b = s.add("string2"); System.out.println("string2 add returns " + b); Iterator i = s.iterator(); while (i.hasNext()) System.out.println(i.next()); } } D:\java SetDemo4 string1 add returns true string2 add returns true string3 add returns true string1 add returns false string2 add returns false string1 string2 string3 D:\ java.util.Iterator 迭代器(interface) •轮循 有序输出(自然顺序)
对象集合(Set) JAVA create a set and add two objects to it; the objects are distinct but have the same displayable string import java.util.*; D:\java SetDemo5 public class SetDemo5 37 public static void main(String args[]){ 37 Set s new HashSet(); s.add("37"); D s.add(new Integer(37)); Iterator i =s.iterator(; while (i.hasNext()) System.out.println(i.next()); 14
14 对象集合(Set) import java.util.*; public class SetDemo5 { public static void main(String args[]) { Set s = new HashSet(); s.add("37"); s.add(new Integer(37)); Iterator i = s.iterator(); while (i.hasNext()) System.out.println(i.next()); } } create a set and add two objects to it; the objects are distinct but have the same displayable string D:\java SetDemo5 37 37 D:\