set的三种遍历

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 
             } 
              ........ 
}