Added findHearts method to HandsOfCards

src/main/java/edu/ntnu/stud/cardgame/HandOfCards.java

@@ -24,4 +24,18 @@ public class HandOfCards {
         mapToInt(PlayingCard::getFace).
         sum();
   }
+
+  public String findHearts() {
+    StringBuilder sb = new StringBuilder();
+
+    hand.stream().
+        map(PlayingCard::getAsString).
+        filter(s -> s.charAt(0) == 'H').
+        forEach(sb::append);
+
+    if (sb.isEmpty()) {
+      return "No hearts";
+    }
+    return sb.toString();
+  }
 }