Acronym: adjust API to use an instance method (#380)

Fixes issue #351.

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

 import java.util.regex.Pattern;
 
 public class Acronym {
-    public static String generate(String phrase){
+    private final String acronym;
+
+    public Acronym(String phrase) {
+        acronym = generateAcronym(phrase);
+    }
+
+    public String get() {
+        return acronym;
+    }
+
+    private String generateAcronym(String phrase){
         final Pattern BREAK_WORDS = Pattern.compile("[A-Z]+[a-z]*|[a-z]+");
         final Matcher matcher = BREAK_WORDS.matcher(phrase);
         final StringBuilder b = new StringBuilder();

exercises/acronym/src/test/java/AcronymTest.java

 
 public class AcronymTest {
 
-
     @Test
     public void fromTitleCasedPhrases() {
         final String phrase = "Portable Network Graphics";
         final String expected = "PNG";
-        assertEquals(expected, Acronym.generate(phrase));
+        assertEquals(expected, new Acronym(phrase).get());
     }
 
     @Ignore
     public void fromOtherTitleCasedPhrases() {
         final String phrase = "Ruby on Rails";
         final String expected = "ROR";
-        assertEquals(expected, Acronym.generate(phrase));
+        assertEquals(expected, new Acronym(phrase).get());
     }
 
     @Ignore
     public void fromInconsistentlyCasedPhrases() {
         final String phrase = "HyperText Markup Language";
         final String expected = "HTML";
-        assertEquals(expected, Acronym.generate(phrase));
+        assertEquals(expected, new Acronym(phrase).get());
     }
 
     @Ignore
     public void fromPhrasesWithPunctuation() {
         final String phrase = "First In, First Out";
         final String expected = "FIFO";
-        assertEquals(expected, Acronym.generate(phrase));
+        assertEquals(expected, new Acronym(phrase).get());
     }
 
     @Ignore
     public void fromOtherPhrasesWithPunctuation() {
         final String phrase = "PHP: Hypertext Preprocessor";
         final String expected = "PHP";
-        assertEquals(expected, Acronym.generate(phrase));
+        assertEquals(expected, new Acronym(phrase).get());
     }
 
     @Ignore
     public void fromPhrasesWithNonAcronymAllCapsWord() {
         final String phrase = "GNU Image Manipulation Program";
         final String expected = "GIMP";
-        assertEquals(expected, Acronym.generate(phrase));
+        assertEquals(expected, new Acronym(phrase).get());
     }
 
     @Ignore
     public void fromPhrasesWithPunctuationAndSentenceCasing() {
         final String phrase = "Complementary metal-oxide semiconductor";
         final String expected = "CMOS";
-        assertEquals(expected, Acronym.generate(phrase));
+        assertEquals(expected, new Acronym(phrase).get());
     }
 
     @Ignore
     public void fromPhraseWithSingleLetterWord() {
         final String phrase = "Cat in a Hat";
         final String expected = "CIAH";
-        assertEquals(expected, Acronym.generate(phrase));
+        assertEquals(expected, new Acronym(phrase).get());
     }
 
 }