Incorporate the class Alphabetical from string package

src/main/java/com/string/Alphabetical.java

@@ -0,0 +1,20 @@
+package com.string;
+
+public class Alphabetical {
+
+    /**
+     * Check if a string is alphabetical order or not
+     *
+     * @param s a string
+     * @return {@code true} if given string is alphabetical order, otherwise {@code false}
+     */
+    public static boolean isAlphabetical(String s) {
+        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))) {
+                return false;
+            }
+        }
+        return true;
+    }
+}

src/test/java/com/string/AlphabeticalTest.java

@@ -0,0 +1,13 @@
+package com.string;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class AlphabeticalTest extends Alphabetical {
+
+    @Test
+    void testAlphabetical() {
+        Assertions.assertEquals(true, isAlphabetical("abc"), "The string is in order");
+        Assertions.assertEquals(false, isAlphabetical("testing"), "The string is not in order");
+    }
+}