3. Different types of Classes, Abstract keyword and Abstract classes (13. Object-oriented programmi

Код abstract Product: https://github.com/AndriiPiatakha/learnit_java_core/blob/master/src/com/itbulls/learnit/javacore/oop/classes/typesofclasses/Product.java Код Cart с Tax и Discount: https://github.com/AndriiPiatakha/learnit_java_core/blob/master/src/com/itbulls/learnit/javacore/oop/classes/Cart.java Код Demo class: https://github.com/AndriiPiatakha/learnit_java_core/blob/master/src/com/itbulls/learnit/javacore/oop/classes/typesofclasses/Demo.java Код Master Product: https://github.com/AndriiPiatakha/learnit_java_core/blob/master/src/com/itbulls/learnit/javacore/oop/classes/typesofclasses/MasterProduct.java Код POJO Product: https://github.com/AndriiPiatakha/learnit_java_core/blob/master/src/com/itbulls/learnit/javacore/oop/classes/Product.java Код User class: https://github.com/AndriiPiatakha/learnit_java_core/blob/master/src/com/itbulls/learnit/javacore/oop/classes/typesofclasses/User.java Код Variant produc: https://github.com/AndriiPiatakha/learnit_java_core/blob/master/src/com/itbulls/learnit/javacore/oop/classes/typesofclasses/VariantProduct.java