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- https://www.geeksforgeeks.org/object-oriented-programming-oops-concept-in-java/
- https://medium.com/learn-how-to-program/chapter-3-what-is-object-oriented-programming-d0a6ec0a7615
- https://www.freecodecamp.org/news/object-oriented-programming-concepts-21bb035f7260/
- https://code.tutsplus.com/tutorials/object-oriented-php-for-beginners--net-12762
- https://www.edureka.co/blog/object-oriented-programming/