diff --git a/src/main/java/com/ctci/arraysandstrings/IsUnique.java b/src/main/java/com/ctci/arraysandstrings/IsUnique.java
index fb975cb..f6e91ed 100644
--- a/src/main/java/com/ctci/arraysandstrings/IsUnique.java
+++ b/src/main/java/com/ctci/arraysandstrings/IsUnique.java
@@ -37,14 +37,37 @@ public static boolean isAllCharactersUniqueAndInASCII(String str) {
         return true;
     }
 
-    private static boolean hasAllUniqueCharactersWhenStringContainsAllLowercase(String s) {
+    /**
+     * Check whether the input string contains different individual characters, lowercase
+     * and in between 'a' and 'z'
+     *
+     * @param str Input string
+     * @return true if all characters are different from each other,lowercase and between 'a' and 'z', otherwise false.
+     */
+    public static boolean isAllCharactersUniqueAndLowercaseAndInAlphabet(String str) {
+        if (str == null
+                || str.isEmpty()
+                || str.length() > 26) {
+            return false;
+        }
+
         int checker = 0;
-        for (int i = 0; i < s.length(); i++) {
-            int charValue = s.charAt(i) - 'a';
-            if ((checker & (1 << charValue)) > 0) {
+        int stringLength = str.length();
+        for (int i = 0; i < stringLength; i++) {
+
+            char character = str.charAt(i);
+            if (!(character >= 'a' && character <= 'z')) {
                 return false;
             }
-            checker |= (1 << charValue);
+
+            int characterIndex  = character - 'a';
+            int singleBitOnPosition = 1 << characterIndex ;
+
+            if ((checker & singleBitOnPosition) > 0) {
+                return false;
+            }
+
+            checker |= singleBitOnPosition; // checker = checker | singleBitOnPosition;
         }
         return true;
     }
@@ -58,11 +81,11 @@ public static void main(String[] args) {
         System.out.println(isAllCharactersUniqueAndInASCII(s));
         System.out.println("-------");
         s = "ram";
-        System.out.println(hasAllUniqueCharactersWhenStringContainsAllLowercase(s));
+        System.out.println(isAllCharactersUniqueAndLowercaseAndInAlphabet(s));
         s = "rama";
-        System.out.println(hasAllUniqueCharactersWhenStringContainsAllLowercase(s));
+        System.out.println(isAllCharactersUniqueAndLowercaseAndInAlphabet(s));
         // not working as the input contains different cases
         s = "ramA";
-        System.out.println(hasAllUniqueCharactersWhenStringContainsAllLowercase(s));
+        System.out.println(isAllCharactersUniqueAndLowercaseAndInAlphabet(s));
     }
 }
diff --git a/src/main/test/com/ctci/arraysandstrings/IsUniqueTest.java b/src/main/test/com/ctci/arraysandstrings/IsUniqueTest.java
index 252faa6..ef373de 100644
--- a/src/main/test/com/ctci/arraysandstrings/IsUniqueTest.java
+++ b/src/main/test/com/ctci/arraysandstrings/IsUniqueTest.java
@@ -6,7 +6,7 @@ public class IsUniqueTest {
 
     @Nested
     @DisplayName("Test cases for isAllCharactersUniqueAndInASCII()")
-    class TestCasesForIsAllCharactersUniqueAndInASCII{
+    class TestCasesForIsAllCharactersUniqueAndInASCII {
 
         @Test
         public void isAllCharactersUniqueAndInASCII_StringIsNull_ReturnFalse() {
@@ -109,4 +109,116 @@ public void isAllCharactersUniqueAndInASCII_ValidString_ReturnTrue() {
                     "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"));
         }
     }
+
+    @Nested
+    @DisplayName("Test cases for isAllCharactersUniqueAndLowercaseAndInAlphabet()")
+    class TestCasesForIsAllCharactersUniqueAndLowercaseAndInAlphabet {
+
+        @Test
+        public void isAllCharactersUniqueAndLowercaseAndInAlphabet_StringIsNull_ReturnFalse() {
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet(null));
+        }
+
+        @Test
+        public void isAllCharactersUniqueAndLowercaseAndInAlphabet_StringIsEmpty_ReturnFalse() {
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet(""));
+        }
+
+        @Test
+        public void isAllCharactersUniqueAndLowercaseAndInAlphabet_StringLengthSmallerOrEqual26_ReturnFalse() {
+            StringBuilder stringBuilder = new StringBuilder();
+
+            for (int i = 97; i <= 122; i++) {   // 'a' -> 'z'
+                stringBuilder.append((char) i);
+            }
+            Assertions.assertTrue(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet(stringBuilder.toString()));
+
+            stringBuilder.setLength(0);
+            for (int i = 100; i <= 120; i++) {   // 'a' -> 'z'
+                stringBuilder.append((char) i);
+            }
+            Assertions.assertTrue(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet(stringBuilder.toString()));
+        }
+
+        @Test
+        public void isAllCharactersUniqueAndLowercaseAndInAlphabet_StringLengthLargerThan26_ReturnFalse() {
+            String a2z = "abcdefghijklmnopqrstuvwxyz";
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet(a2z + (char) 96)); // 96 => `
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet(a2z + (char) 123)); // 123 => {
+        }
+
+        @Test
+        public void isAllCharactersUniqueAndLowercaseAndInAlphabet_Beyond_a2z_ReturnFalse() {
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("GH@"));
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("{} "));
+
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("ááb"));
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("ÁÁb"));
+
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("1123456"));
+        }
+
+        @Test
+        public void isAllCharactersUniqueAndLowercaseAndInAlphabet_DuplicateAtHead_ReturnFalse() {
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("aab"));
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("AAb"));
+
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("ááb"));
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("ÁÁb"));
+
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("1123456"));
+        }
+
+        @Test
+        public void isAllCharactersUniqueAndLowercaseAndInAlphabet_DuplicateAtMiddle_ReturnFalse() {
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("abcbd"));
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("aBcBd"));
+
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("aưcưd"));
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("aƯcƯd"));
+
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("123436"));
+        }
+
+        @Test
+        public void isAllCharactersUniqueAndLowercaseAndInAlphabet_DuplicateAtTail_ReturnFalse() {
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("aba"));
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("AbA"));
+
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("ăbă"));
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("ĂbĂ"));
+
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("1234566"));
+        }
+
+        @Test
+        public void isAllCharactersUniqueAndLowercaseAndInAlphabet_OnlyOneCharacter_ReturnTrue() {
+            for (int i = 97; i <= 122; i++) {
+                Assertions.assertTrue(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet(String.valueOf((char) i)));
+            }
+        }
+
+        @Test
+        public void isAllCharactersUniqueAndLowercaseAndInAlphabet_OnlyOneCharacter_ReturnFalse() {
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("A"));
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("á"));
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("Ô"));
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("€"));
+        }
+
+        @Test
+        public void isAllCharactersUniqueAndLowercaseAndInAlphabet_InvalidString_ReturnFalse() {
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("ۇ"));
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("áÂ"));
+            Assertions.assertFalse(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("aB"));
+        }
+
+        @Test
+        public void isAllCharactersUniqueAndLowercaseAndInAlphabet_ValidString_ReturnTrue() {
+            Assertions.assertTrue(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("mwq"));
+            Assertions.assertTrue(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("fwoklt"));
+            Assertions.assertTrue(IsUnique.isAllCharactersUniqueAndLowercaseAndInAlphabet("abcdefghijklmnopqrstuvwxyz"));
+        }
+    }
+
 }