part 4-1 parity with Finnish translation

ConcernedHobbit · web-flow · commit 4e600536b82b · 2022-01-08T20:36:10.000+02:00
adds missing translation in Whistle exercise details
diff --git a/data/part-4/1-introduction-to-object-oriented-programming.md b/data/part-4/1-introduction-to-object-oriented-programming.md
@@ -607,6 +607,8 @@ Pillin tulee toimia seuraavasti. -->
 
 Create a class named `Whistle`. Add the variable `private String sound` to the class. After that, create the constructor `public Whistle(String whistleSound)`, which is used to create a new whistle that's given a sound.
 
+Then create the method `public void sound()` that prints the whistle's sound.
+
 <!-- ```java
 Pilli sorsapilli = new Pilli("Kvaak");
 Pilli kukkopilli = new Pilli("Peef");
