Add MostFrequentWordsImpl

src/main/java/ru/ilug/c9_most_frequent_words/MainTest.java

@@ -8,7 +8,7 @@ import java.util.Map;
 public class MainTest {
 
     public static void main(String[] args) {
-        MostFrequentWords mostFrequentWords = null;
+        MostFrequentWords mostFrequentWords = new MostFrequentWordsImpl();
 
         Map<String, Integer> result = mostFrequentWords.getNWords("На дворе трава, на траве дрова. Не руби дрова на траве двора!", 3);
         log.info("3 most frequent words: {}", result);

src/main/java/ru/ilug/c9_most_frequent_words/MostFrequentWordsImpl.java

@@ -0,0 +1,24 @@
+package ru.ilug.c9_most_frequent_words;
+
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+public class MostFrequentWordsImpl implements MostFrequentWords {
+
+    @Override
+    @SuppressWarnings("unchecked")
+    public Map<String, Integer> getNWords(String text, int count) {
+        return Arrays.stream(text.replaceAll("[.,!]", "").split(" "))
+                .collect(
+                        Collectors.groupingBy(c -> c,
+                                Collectors.collectingAndThen(Collectors.toList(), List::size)
+                        )
+                ).entrySet().stream()
+                .sorted(Comparator.comparingInt(e -> ((Map.Entry<String, Integer>)e).getValue()).reversed())
+                .limit(count)
+                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
+    }
+}