public class ReverseTester
{
   public static void main(String[] args)
   {
      StringBuilder words = new StringBuilder("deliver star maps");

      char[] word1 = words.substring(0, 7).toCharArray();
      char[] word2 = words.substring(8, 12).toCharArray();
      char[] word3 = words.substring(13, 17).toCharArray();

      StringBuilder reversed = new StringBuilder();
      for(int i = word3.length - 1; i >= 0; i--)
      {
         reversed.append(word3[i]);
      }
      reversed.append(' ');
      for(int i = word2.length - 1; i >= 0; i--)
      {
          reversed.append(word2[i]);
      }
      reversed.append(' ');
      for(int i = word1.length - 1; i >= 0; i--)
      {
          reversed.append(word1[i]);
      }

      System.out.println(reversed);
      System.out.println("Expected: spam rats reviled");
  }
}