public class mySet {
	public static void main(String[] args) {
		Set set=new HashSet();
		set.add(new student("小花",27));
		set.add(new student("小刚",25));
		set.add(new student("小民",24));
		set.add(new student("小明",23));
		
		Iterator iter=set.iterator();
		String str;
		while(iter.hasNext()){
			str=((student)iter.next()).name;
			System.out.println(str);
		}
//		System.out.println(set.size());
	}
	
}

class student1{
	String name;
	int id;
	public student1(String name, int id) {
		super();
		this.name = name;
		this.id = id;
	}
	
	
}

		Set set = map.keySet();
		Iterator iter = set.iterator();
		while(iter.hasNext()){
			System.out.println(((student)iter.next()).name);//打印出map中的键(1，2，3)
		}