Java泛型限定 草稿

import java.util.*;

class GD6
{
　　public static void main(String[] args)
{
ArrayList<Person> a = new ArrayList<Person>();
a.add(new Person("a"));
a.add(new Person("b"));
a.add(new Person("c"));

ArrayList<Stu> al1 = new ArrayList<Stu>();
al1.add(new Stu("A"));
al1.add(new Stu("B"));
al1.add(new Stu("C"));
printCln(a);
}

public static void printCln(ArrayList<Person> al)
{
Iterator<Person> it = al.iterator();
while(it.hasNext())
{
System.out.println(it.next().getName());
}
}
}

class Person
{
String name;
String getName()
{
return this.name;
}
Person(String name){
this.name = name;
}
}

class Stu extends Person
{
String name;
Stu(String name)
{
super(name);
}
}