added example code for BAEL-2418 (#5882)

* added example code for BAEL-2366

* moved example code for BAEL-2366

* example code for BAEL-1961

* moved example code into integration test

* updated the test assertions

* refactor the spring boot persistence mongodb module

* remove redundant example code

* declared the spring boot persistence module in the root pom

* fixed issue with non-imported file

* added example code for BAEL-2418

core-java/src/main/java/com/baeldung/basicsyntax/SimpleAddition.java

@@ -0,0 +1,11 @@
+package com.baeldung.basicsyntax;
+
+public class SimpleAddition {
+
+    public static void main(String[] args) {
+        int a = 10;
+        int b = 5;
+        double c = a + b;
+        System.out.println( a + " + " + b + " = " + c);
+    }
+}