Inline optional

tcr-roman-numerals/src/main/java/fr/ippon/kata/numeral/Numerals.java

@@ -4,13 +4,17 @@ import java.util.Map.Entry;
 import java.util.NavigableMap;
 import java.util.Optional;
 import java.util.TreeMap;
+import java.util.function.Function;
 
 public class Numerals {
   private static final NavigableMap<Integer, String> CONVERSIONS = buildConversions();
 
   public static String toRoman(int arabic) {
-    Optional<Entry<Integer, String>> highestKnownConversion = Optional.ofNullable(CONVERSIONS.floorEntry(arabic));
-    return highestKnownConversion.map(conversion -> conversion.getValue() + toRoman(arabic - conversion.getKey())).orElse("");
+    return Optional.ofNullable(CONVERSIONS.floorEntry(arabic)).map(romanRepresentation(arabic)).orElse("");
+  }
+
+  private static Function<Entry<Integer, String>, String> romanRepresentation(int arabic) {
+    return conversion -> conversion.getValue() + toRoman(arabic - conversion.getKey());
   }
 
   private static NavigableMap<Integer, String> buildConversions() {