黑马程序员-学习日记（泛型）

import java.util.*;
//15天13听的不是很懂
class GenericDemo 
{
    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"));
       
        Iterator it = al.iterator();
        while(it.hasNext())
        {
            String s = it.next(); //注意这里缺少了向下转型
            System.out.println(s);
        }

        ArrayList<Stu> al1 = new ArrayList<Stu>();
        al1.add(new Stu("A"));

        al1.add(new Stu("B"));
        al1.add(new Stu("C"));
        printCln(al1);
    }
}