package com.bjpowernode.test;   
 import java.util.HashSet; 
 import java.util.Iterator; 
 import java.util.Set;   
 /** 
 * 一个不包含重复元素的 collection。更确切地讲，set 不包含满足 e1.equals(e2) 的元素对 e1 和 e2， 
 * @author Owner 
 * 
 */ 
 public class SetTest2 {   
   public static void main(String[] args) { 
     Set<String> set = new HashSet<String>();       
     set.add("a"); 
     set.add("b"); 
     set.add("c"); 
     set.add("d"); 
    set.add("e");       
     set.add("e");//不能放入重复数据 
     /** 
     * 遍历方法一，迭代遍历 
     */ 
     for(Iterator<String> iterator = set.iterator();iterator.hasNext();){ 
       System.out.print(iterator.next()+" "); 
     } 
     System.out.println(); 
     System.out.println("********************"); 
     /** 
     * for增强循环遍历 
     */ 
     for(String value : set){ 
       System.out.print(value+" "); 
     } 
   } 
 } 

Set<String> set = new TreeSet<String>();  
     set.add("f"); 
     set.add("a"); 
     set.add("b"); 
     set.add("c"); 
     set.add("d"); 
     set.add("e"); 
     System.out.println(set); 

package com.bjpowernode.test;   
 import java.util.Comparator; 
 import java.util.Iterator; 
 import java.util.Set; 
 import java.util.TreeSet;   
 public class TreeSetTest3 {   
   public static void main(String[] args) { 
     Set<String> set = new TreeSet<String>(new MyComparator());       
     set.add("a"); 
     set.add("b"); 
     set.add("c"); 
     set.add("d"); 
     set.add("e"); 
     set.add("A");       
     for(Iterator<String> iterator = set.iterator();iterator.hasNext();){ 
       System.out.print(iterator.next()+" "); 
     } 
   } 
 }   
 class MyComparator implements Comparator<String>{   
   @Override 
   public int compare(String o1, String o2) {       
     return o2.compareTo(o1);//降序排列 
   }  
 } 

package com.bjpowernode.test;  
 import java.util.Comparator; 
 import java.util.Iterator; 
 import java.util.Set; 
 import java.util.TreeSet; 
 public class TreeSetTest2 { 
   public static void main(String[] args) { 
     Set<Person> set = new TreeSet<Person>(new PersonComparator()); 
     Person p1 = new Person(10); 
     Person p2 = new Person(20); 
     Person p3 = new Person(30); 
     Person p4 = new Person(40); 
     set.add(p1); 
    set.add(p2); 
     set.add(p3); 
     set.add(p4); 
      
     for(Iterator<Person> iterator = set.iterator();iterator.hasNext();){ 
       System.out.print(iterator.next().score+" "); 
     } 
   } 
 } 
 class Person{ 
   int score; 
   public Person(int score){ 
     this.score = score; 
   } 
   public String toString(){ 
     return String.valueOf(this.score); 
   } 
 }  
 class PersonComparator implements Comparator<Person>{ 
   @Override 
   public int compare(Person o1, Person o2) { 
      
     return o1.score - o2.score; 
   }  
 }