import java.util.Arrays;

public class SwapHalves
{
   public static void main(String[] args)
   {
      int[] values = { 9, 13, 21, 4, 11, 7, 1, 3 };

      int i = 0;
      int j = values.length / 2;
      while (i < values.length / 2)
      {
         // Swap values at positions i and j
         int temp = values[i];
         values[i] = values[j];
         values[j] = temp;

         i++;
         j++;
      }

      System.out.println(Arrays.toString(values));
   }
}