1  import java.util.ArrayList;

  2  

  3  public class WildcardDemo

  4  {

  5     public static <E> void addAll(ArrayList<E> lst, ArrayList<? extends E> other)

  6     // public static <E> void addAll(ArrayList<E> lst, ArrayList<E> other)

  7     // doesn't work with Student array list

  8     {

  9        for (E e : other)

 10        {

 11           lst.add(e);

 12        }

 13     }

 14  

 15     public static <E extends Comparable<? super E>> E max(ArrayList<E> a)

 16     // public static <E extends Comparable<E>> E max(ArrayList<E> a) 

 17     // doesn't work with Student array list

 18     {

 19        E largest = a.get(0);

 20        for (int i = 1; i < a.size(); i++)

 21        {

 22           if (a.get(i).compareTo(largest) > 0) 

 23           {

 24              largest = a.get(i);

 25           }

 26        }

 27        return largest;

 28     }

 29  

 30     public static void main(String[] args)

 31     {

 32        ArrayList<Student> students = new ArrayList<Student>();

 33        students.add(new Student("Fred", "CS"));

 34        students.add(new Student("Ann", "Bio"));

 35        students.add(new Student("Sue", "CS"));

 36  

 37        ArrayList<Person> people =  new ArrayList<Person>();

 38        people.add(new Person("Harry"));

 39  

 40        addAll(people, students);

 41        System.out.println(people);

 42  

 43        System.out.println(max(students));      

 44     }

 45  }