HashSetコレクション紹介

package com.itheima.demo02.Set;
import java.util.HashSet;import java.util.Iterator;import java.util.Set;
/*

java.util.Set   extends Collection  
Set     :
    1.          
    2.    ,        ,        for    
java.util.HashSet   implements Set  
HashSet  :
     1.          
     2.    ,        ,        for    
     3.        ,                  
     4.          (         )

*/public class Demo01Set {

public static void main(String[] args) {
    Set set = new HashSet<>();
    //  add          
    set.add(1);
    set.add(3);
    set.add(2);
    set.add(1);
    //       set  
    Iterator it = set.iterator();
    while (it.hasNext()){
        Integer n = it.next();
        System.out.println(n);//1,2,3
    }
    //    for  set  
    System.out.println("-----------------");
    for (Integer i : set) {
        System.out.println(i);
    }
}

}