1. import java.util.*;
   
2. class Person
   
3. {
   
4. private String name;
   
5. Person(String name)
   
6. {
   
7. this.name=name;
   
8. }
   
9. 
   
10. public String getName()
    
11. {
    
12. return name;
    
13. }
    
14. }
    
15. 
    
16. class Student extends Person
    
17. {
    
18. 
    
19. Student(String name)
    
20. {
    
21. super(name);
    
22. }
    
23. 
    
24. 
    
25. }
    
26. 
    
27. public class Gener6
    
28. {
    
29. public static void main(String[]args)
    
30. {
    
31. ArrayList<Person>al =new ArrayList<Person>();
    
32. al.add(new Person("abc01"));
    
33. al.add(new Person("abc02"));
    
34. al.add(new Person("abc03"));
    
35. al.add(new Person("abc04"));
    
36. print(al);
    
37. System.out.println();
    
38. ArrayList<Student>al2=new ArrayList<Student>();
    
39. al2.add(new Student("def01"));
    
40. al2.add(new Student("def02"));
    
41. al2.add(new Student("def03"));
    
42. al2.add(new Student("def04"));
    
43. print(al2);
    
44. }
    
45. 
    
46. public static void print(Collection<? extends Person>al)
    
47. {
    
48. Iterator<? extends Person> it=al.iterator();
    
49. while(it.hasNext())
    
50. {
    
51. System.out.print(" "+it.next().getName());
    
52. }
    
53. }
    
54. }

复制代码

错误好像是说33行找不到特定方法，真不知道原因是什么？

我把你的代码运行了一下，没问题，

这个我验证了一下，没有问题，可以放心使用
import java.util.*;
class Person
{
private String name;
Person(String name)
{
this.name=name;
}
String getName()
{
return name;
}
}
class Student extends Person
{
Student(String name)
{
super(name);
}

}
class Gener6
{
public static void main(String[]args)
{
ArrayList<Person>al =new ArrayList<Person>();
al.add(new Person("abc01"));
al.add(new Person("abc02"));
al.add(new Person("abc03"));
al.add(new Person("abc04"));
print(al);
System.out.println();
ArrayList<Student>al2=new ArrayList<Student>();
al2.add(new Student("def01"));
al2.add(new Student("def02"));
al2.add(new Student("def03"));
al2.add(new Student("def04"));
print(al2);
}
public static void print(Collection<? extends Person>al)
{
Iterator<? extends Person> it=al.iterator();
while(it.hasNext())
{
System.out.print(" "+it.next().getName());
}
}
}