diff --git a/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/bookstore/Book.java b/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/bookstore/Book.java
new file mode 100644
index 0000000000..83ed76bab0
--- /dev/null
+++ b/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/bookstore/Book.java
@@ -0,0 +1,21 @@
+// The next line is commented out to avoid the code to fail the build.
+// package com.baeldung;
+
+/**
+* If the below package declaration is commented out and the above incorrect package 
+* declaration is uncommented, then the problem will replicate.
+*/
+package com.baeldung.bookstore;
+
+public class Book {
+
+    private String title;
+    private String author;
+    private long isbn;
+    
+    public Book(String title, String author, long isbn) {
+        this.title = title;
+        this.author = author;
+        this.isbn = isbn;
+    }
+}
diff --git a/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/bookstore/LibraryAdmin.java b/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/bookstore/LibraryAdmin.java
new file mode 100644
index 0000000000..9abd654589
--- /dev/null
+++ b/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/bookstore/LibraryAdmin.java
@@ -0,0 +1,14 @@
+package com.baeldung.bookstore;
+
+import java.util.Random;
+
+public class LibraryAdmin {
+
+    public Book createBook(String title, String author) {
+
+        final long isbn = new Random().nextLong();
+
+        return new Book(title, author, isbn);
+    }
+    
+}
\ No newline at end of file