acronym: standardize starter implementation

exercises/acronym/src/example/java/Acronym.java

 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
-public class Acronym {
+final class Acronym {
+
     private final String acronym;
 
-    public Acronym(String phrase) {
+    Acronym(String phrase) {
         acronym = generateAcronym(phrase);
     }
 
-    public String get() {
+    String get() {
         return acronym;
     }
 
         }
         return b.toString().toUpperCase();
     }
-}
+
+}

exercises/acronym/src/main/java/Acronym.java

+final class Acronym {
+
+    Acronym(String phrase) {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+    }
+
+    String get() {
+        throw new UnsupportedOperationException("Delete this statement and write your own implementation.");
+    }
+
+}