Fix error in CheckCapitalUsage solution

Author: andrei-punko

src/main/java/by/andd3dfx/string/CheckCapitalUsage.java

@@ -1,6 +1,7 @@
 package by.andd3dfx.string;
 
-import java.util.Set;
+import java.util.HashSet;
+import java.util.List;
 import java.util.regex.Pattern;
 
 /**
@@ -33,7 +34,7 @@ public boolean isCapitalUsedProperly(String word) {
         var lowercase = word.toLowerCase();
         var onlyFirstLetterCapitalized = buildWordWithFirstLetterCapitalized(word);
 
-        return Set.of(uppercase, lowercase, onlyFirstLetterCapitalized)
+        return new HashSet<>(List.of(uppercase, lowercase, onlyFirstLetterCapitalized))
                 .contains(word);
     }
 

src/test/java/by/andd3dfx/string/CheckCapitalUsageTest.java

@@ -17,6 +17,8 @@ public void setUp() throws Exception {
 
     @Test
     public void isCapitalUsedProperly() {
+        assertTrue(checkCapitalUsage.isCapitalUsedProperly("a"));
+        assertTrue(checkCapitalUsage.isCapitalUsedProperly("A"));
         assertTrue(checkCapitalUsage.isCapitalUsedProperly("USA"));
         assertTrue(checkCapitalUsage.isCapitalUsedProperly("Google"));
         assertTrue(checkCapitalUsage.isCapitalUsedProperly("leetcode"));
@@ -26,6 +28,8 @@ public void isCapitalUsedProperly() {
 
     @Test
     public void isCapitalUsedProperly_withRegex() {
+        assertTrue(checkCapitalUsage.isCapitalUsedProperly_withRegex("a"));
+        assertTrue(checkCapitalUsage.isCapitalUsedProperly_withRegex("A"));
         assertTrue(checkCapitalUsage.isCapitalUsedProperly_withRegex("USA"));
         assertTrue(checkCapitalUsage.isCapitalUsedProperly_withRegex("Google"));
         assertTrue(checkCapitalUsage.isCapitalUsedProperly_withRegex("leetcode"));