BAEL-838 Tiny change to keep code consistant. Return null or empty. (#1866)

* Code for Dependency Injection Article.

* Added Java based configuration. Downloaded formatter.xml and reformatted
all changed files. Manually changed tab into 4 spaces in XML
configuration files.

* BAEL-434 - Spring Roo project files generated by Spring Roo. No
formatting applied. Added POM, java and resources folders.

* Moved project from roo to spring-roo folder.

* BAEL-838 Initial code showing how to remove last char - helper class and tests.

* BAEL-838 Corrected Helper class and associated empty string test case. Added StringUtils.substing tests.

* BAEL-838 Refromatted code using formatter.xml. Added Assert.assertEquals import. Renamed test to follow convention. Reordered tests.

* BAEL-838 - Added regex method and updated tests.

* BAEL-838 Added new line examples.

* BAEL-838 Renamed RemoveLastChar class to StringHelper and added Java8 examples. Refactord code.

* BAEL-838 Changed method names

* BAEL-838 Tiny change to keep code consistant. Return null or empty.

* BAEL-838 Removed unresolved conflict.

core-java/src/main/java/com/baeldung/string/StringHelper.java

@@ -21,6 +21,6 @@ public class StringHelper {
     public static String removeLastCharRegexOptional(String s) {
         return Optional.ofNullable(s)
             .map(str -> str.replaceAll(".$", ""))
-            .orElse(null);
+            .orElse(s);
     }
 }