From 1ea9f49a7478187ec1e6bbde6be2a48cf9e89dbf Mon Sep 17 00:00:00 2001
From: Ayesha Rathnayake <rasanjaleea36@gmail.com>
Date: Tue, 7 Oct 2025 15:14:39 +0530
Subject: [PATCH 1/4] Enhance Alphabetical.isAlphabetical with null and empty
 string check

---
 .../java/com/thealgorithms/strings/Alphabetical.java  | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/main/java/com/thealgorithms/strings/Alphabetical.java b/src/main/java/com/thealgorithms/strings/Alphabetical.java
index ef2974eb427d..7abc9abfb3bb 100644
--- a/src/main/java/com/thealgorithms/strings/Alphabetical.java
+++ b/src/main/java/com/thealgorithms/strings/Alphabetical.java
@@ -21,12 +21,17 @@ private Alphabetical() {
      * @return {@code true} if all characters are in alphabetical order (case-insensitive), otherwise {@code false}
      */
     public static boolean isAlphabetical(String s) {
+        if (s == null || s.isEmpty()) {
+            return false;
+        }
         s = s.toLowerCase();
-        for (int i = 0; i < s.length() - 1; ++i) {
-            if (!Character.isLetter(s.charAt(i)) || s.charAt(i) > s.charAt(i + 1)) {
+        for (int i = 0; i < s.length() - 1; i++) {
+            char current = s.charAt(i);
+            char next = s.charAt(i + 1);
+            if (!Character.isLetter(current) || current > next) {
                 return false;
             }
         }
-        return !s.isEmpty() && Character.isLetter(s.charAt(s.length() - 1));
+        return Character.isLetter(s.charAt(s.length() - 1));
     }
 }

From 7c1940ea758801316405ff279ab3456f4324ea5c Mon Sep 17 00:00:00 2001
From: Ayesha Rathnayake <rasanjaleea36@gmail.com>
Date: Tue, 7 Oct 2025 15:38:18 +0530
Subject: [PATCH 2/4] Add test cases for strings ending with non-letter to fix
 coverage

---
 .../thealgorithms/strings/AlphabeticalTest.java | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java b/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java
index 7b41e11ef22f..b8dd8610fe1d 100644
--- a/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java
+++ b/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java
@@ -8,8 +8,23 @@
 public class AlphabeticalTest {
 
     @ParameterizedTest(name = "\"{0}\" → Expected: {1}")
-    @CsvSource({"'abcdefghijklmno', true", "'abcdxxxyzzzz', true", "'123a', false", "'abcABC', false", "'abcdefghikjlmno', false", "'aBC', true", "'abc', true", "'xyzabc', false", "'abcxyz', true", "'', false", "'1', false"})
+    @CsvSource({
+            "'abcdefghijklmno', true",
+            "'abcdxxxyzzzz', true",
+            "'123a', false",
+            "'abcABC', false",
+            "'abcdefghikjlmno', false",
+            "'aBC', true",
+            "'abc', true",
+            "'xyzabc', false",
+            "'abcxyz', true",
+            "'', false",
+            "'1', false",
+            "'abc!', false",    // <--- string ending with non-letter
+            "'ABc1', false"     // <--- another example
+    })
     void testIsAlphabetical(String input, boolean expected) {
         assertEquals(expected, Alphabetical.isAlphabetical(input));
     }
+
 }

From d6222db7af65238d5e20540a72b6b0e9d095823a Mon Sep 17 00:00:00 2001
From: Ayesha Rathnayake <rasanjaleea36@gmail.com>
Date: Tue, 7 Oct 2025 15:41:46 +0530
Subject: [PATCH 3/4] Add test cases for strings ending with non-letter to fix
 patch coverage

---
 src/test/java/com/thealgorithms/strings/AlphabeticalTest.java | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java b/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java
index b8dd8610fe1d..a3f8afa8160c 100644
--- a/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java
+++ b/src/test/java/com/thealgorithms/strings/AlphabeticalTest.java
@@ -20,8 +20,8 @@ public class AlphabeticalTest {
             "'abcxyz', true",
             "'', false",
             "'1', false",
-            "'abc!', false",    // <--- string ending with non-letter
-            "'ABc1', false"     // <--- another example
+            "'abc!', false",   // <-- missing coverage
+            "'ABc1', false"    // <-- optional extra
     })
     void testIsAlphabetical(String input, boolean expected) {
         assertEquals(expected, Alphabetical.isAlphabetical(input));

From ca212b48fae95f614037dcc6ec1ac3f76734294d Mon Sep 17 00:00:00 2001
From: Ayesha Rathnayake <rasanjaleea36@gmail.com>
Date: Tue, 7 Oct 2025 15:48:53 +0530
Subject: [PATCH 4/4] Apply clang-format to AlphabeticalTest.java

---
 pom.xml | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/pom.xml b/pom.xml
index 938fb41088dc..9319178c0bf2 100644
--- a/pom.xml
+++ b/pom.xml
@@ -55,6 +55,13 @@
             <artifactId>commons-collections4</artifactId>
             <version>4.5.0</version>
         </dependency>
+
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <version>5.9.3</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>