Added at function

src/main/java/strman/Strman.java

@@ -1,5 +1,6 @@
 package strman;
 
+import java.util.Optional;
 import java.util.StringJoiner;
 
 /**
@@ -26,7 +27,7 @@ public interface Strman {
      * @param appends an array of strings to append
      * @return full String
      */
-    static String appendArray(String value, String[] appends) {
+    static String appendArray(final String value, final String[] appends) {
         if (value == null) {
             throw new IllegalArgumentException("'value' should be not null.");
         }
@@ -39,4 +40,24 @@ public interface Strman {
         }
         return value + joiner.toString();
     }
+
+    /**
+     * Get the character at index. This method will take care of negative indexes.
+     * The valid value of index is between -(length-1) to (length-1).
+     * For values which don't fall under this range Optional.empty will be returned.
+     *
+     * @param value input value
+     * @param index location
+     * @return an Optional String if found else empty
+     */
+    static Optional<String> at(final String value, int index) {
+        if (value == null || value.isEmpty()) {
+            return Optional.empty();
+        }
+        int length = value.length();
+        if (index < 0) {
+            index = length + index;
+        }
+        return (index < length && index >= 0) ? Optional.of(String.valueOf(value.charAt(index))) : Optional.empty();
+    }
 }