import java.util.*;
class Treeset
{
 public static void main(String[] args)
 {
  TreeSet t = new TreeSet();
  t.add(new student("a1",15));
  t.add(new student("a2",15));
  t.add(new student("a1",15));
  t.add(new student("a3",16));
  t.add(new student("a3",18));
  for(Iterator it = t.iterator();it.hasNext();)
  {
   student tt = (student)it.next();//强制转成学生类型
   sop(tt.getName()+","+tt.getAge());
  }
 }
 public static void sop(Object obj)
 {
  System.out.println(obj);
 }
}
class student implements Comparable//接口让学生具有比较性
{
 private String name;
 private int age;
 student(String name,int age)
 {
  this.name = name;
  this.age = age;
 }
 public int compareTo(Object obj)
 {
  if(!(obj instanceof student))
   throw new RuntimeException("不是学生");
  student t = (student)obj;
  if(this.age > t.age)
   return 1;
  if(this.age==t.age)
   return this.name.compareTo(t.name);//如果年龄相同，在比较姓名排序
  return -1;
 }
 public String getName()
 {
  return name;
 }
 public int getAge()
 {
  return age;
 }
}