refactoring: Issues #2326 and #2325 (#2327)

* Fix comment typo #2325

* Minor enchancements to flyweight #2326

* Minor enchancements to flyweight #2326

feature-toggle/src/main/java/com/iluwatar/featuretoggle/user/UserGroup.java

@@ -48,7 +48,7 @@ public class UserGroup {
    */
   public static void addUserToFreeGroup(final User user) throws IllegalArgumentException {
     if (paidGroup.contains(user)) {
-      throw new IllegalArgumentException("User all ready member of paid group.");
+      throw new IllegalArgumentException("User already member of paid group.");
     } else {
       if (!freeGroup.contains(user)) {
         freeGroup.add(user);
@@ -65,7 +65,7 @@ public class UserGroup {
    */
   public static void addUserToPaidGroup(final User user) throws IllegalArgumentException {
     if (freeGroup.contains(user)) {
-      throw new IllegalArgumentException("User all ready member of free group.");
+      throw new IllegalArgumentException("User already member of free group.");
     } else {
       if (!paidGroup.contains(user)) {
         paidGroup.add(user);

flyweight/src/main/java/com/iluwatar/flyweight/PotionFactory.java

@@ -46,27 +46,25 @@ public class PotionFactory {
       switch (type) {
         case HEALING:
           potion = new HealingPotion();
-          potions.put(type, potion);
           break;
         case HOLY_WATER:
           potion = new HolyWaterPotion();
-          potions.put(type, potion);
           break;
         case INVISIBILITY:
           potion = new InvisibilityPotion();
-          potions.put(type, potion);
           break;
         case POISON:
           potion = new PoisonPotion();
-          potions.put(type, potion);
           break;
         case STRENGTH:
           potion = new StrengthPotion();
-          potions.put(type, potion);
           break;
         default:
           break;
       }
+      if (potion != null) {
+        potions.put(type, potion);
+      }
     }
     return potion;
   }

flyweight/src/test/java/com/iluwatar/flyweight/AlchemistShopTest.java

@@ -28,6 +28,7 @@ import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 
 import java.util.ArrayList;
+import java.util.HashSet;
 import org.junit.jupiter.api.Test;
 
 /**
@@ -55,8 +56,6 @@ class AlchemistShopTest {
 
     // There are 13 potion instances, but only 5 unique instance types
     assertEquals(13, allPotions.size());
-    assertEquals(5, allPotions.stream().map(System::identityHashCode).distinct().count());
+    assertEquals(5, new HashSet<>(allPotions).size());
-
   }
-
 }