set集合遍历

对 set 的遍历  

1.迭代遍历：
Set<String> set = new HashSet<String>();
Iterator<String> it = set.iterator();
while (it.hasNext()) {
  String str = it.next();
  System.out.println(str);
}  

2.for循环遍历：
for (String str : set) {
      System.out.println(str);
}  

优点还体现在泛型 假如 set中存放的是Object  

Set<Object> set = new HashSet<Object>();
for循环遍历：
for (Object obj: set) {
      if(obj instanceof Integer){
                int aa= (Integer)obj;
             }else if(obj instanceof String){
               String aa = (String)obj
             }  

}