Update free-programming-books-subjects.md (#10161)

* Update free-programming-books-subjects.md

Added a free book on OOP named Learn Object Oriented Thinking and Programming by Rudolf Pecinovsky

* Update free-programming-books-subjects.md

* Update free-programming-books-subjects.md

* Update free-programming-books-subjects.md

* Update free-programming-books-subjects.md

* Update free-programming-books-subjects.md

books/free-programming-books-subjects.md

@@ -664,6 +664,7 @@ Books that cover a specific programming language can be found in the [BY PROGRAM
 ### Object Oriented Programming
 
 * [Object Oriented Programming](https://www.cl.cam.ac.uk/teaching/0910/OOProg/OOP.pdf) - Robert Harle (PDF)
+* [OOP – Learn Object Oriented Thinking and Programming](https://files.bruckner.cz/be2a5b2104bf393da7092a4200903cc0/PecinovskyOOP.pdf) - Rudolf Pecinovsky (PDF) 
 
 
 ### Open Source Ecosystem