      1  public class UnsafeDemo

      2  {

      3     public static void main(String[] args)

      4     {

      5        // Here, we use the linked list class from Chapter 16

      6        LinkedList numbers = new LinkedList();

      7        numbers.addFirst(1);

      8        numbers.addFirst(2);

      9        numbers.addFirst(3);

     10        print(numbers);

     11        System.out.println("Sum: " + sum(numbers));

     12        numbers.addFirst("4"); // No error message

     13        print(numbers); // No error

     14        System.out.println("Sum: " + sum(numbers));

     15           // ClassCastException

     16     }

     17

     18     public static void print(LinkedList lst)

     19     {

     20        ListIterator iter = lst.listIterator();

     21        while (iter.hasNext())

     22        {

     23           System.out.print(iter.next() + " ");

     24        }

     25        System.out.println();

     26     }

     27

     28     public static int sum(LinkedList lst)

     29     {

     30        int sum = 0;

     31        ListIterator iter = lst.listIterator();

     32        while (iter.hasNext())

     33        {

     34           sum = sum + (Integer) iter.next();

     35        }

     36        return sum;

     37     }

     38  }