Use the following file:

SentenceTester.java

/**
   A tester class for Sentence.
*/
public class SentenceTester
{
   public static void main(String[] args)
   {
      Sentence greeting = new Sentence("Hello!");
      greeting.reverse();
      System.out.println(greeting.getText());
      System.out.println("Expected: !olleH");
   }
}