class Person
{
    String name;
    int age;
    
    Person(String name, int age)
    {
        this.name=name;
        this.age=age;    
    }
    
    String toPrint(Object obj)
    {
        if( !(obj instanceof Person) )//如果obj不是Person的实例，不同的对象，就没有比较的意义
        {                             
            return "无效比较！";
        }
        Person p = (Person)obj;//而且当obj不是Person的实例，在进行类型转换时，会抛出异常
        return (this.age > p.age)? this.name:p.name;
    }
}

public class Main
{
  public static void main(String [] args)
  {
      Person p1 = new Person("Allen",20);
      Person p2 = new Person("Jack",30);
      System.out.println( p1.toPrint(p2) );   
      System.out.println( p1.toPrint(new String("hello")) );  
  }
}