1  import java.util.ArrayList;

  2  import java.util.Iterator;

  3  

  4  public class UnsafeDemo2

  5  {

  6     public static void main(String[] args)

  7     {

  8        ArrayList<Integer> numbers = new ArrayList<Integer>();

  9        numbers.add(1);

 10        numbers.add(2);

 11        numbers.add(3);

 12        print(numbers);

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

 14        numbers.add("4"); // Compiler error message

 15        print(numbers); 

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

 17     }

 18  

 19     public static void print(ArrayList<Integer> lst)

 20     {

 21        Iterator<Integer> iter = lst.iterator();

 22        while (iter.hasNext())

 23        {

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

 25        }

 26        System.out.println();

 27     }

 28  

 29     public static int sum(ArrayList<Integer> lst)

 30     {

 31        int sum = 0;

 32        Iterator<Integer> iter = lst.iterator();

 33        while (iter.hasNext())

 34        {

 35           sum = sum + iter.next(); // No cast needed

 36        }

 37        return sum;

 38     }

 39  }