Add Abstract Class and Methods

Author: Hardvan

14_Abstract_Class_and_Methods/README.md

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+## Getting Started
+
+Welcome to the VS Code Java world. Here is a guideline to help you get started to write Java code in Visual Studio Code.
+
+## Folder Structure
+
+The workspace contains two folders by default, where:
+
+-`src`: the folder to maintain sources
+-`lib`: the folder to maintain dependencies
+
+Meanwhile, the compiled output files will be generated in the `bin` folder by default.
+
+> If you want to customize the folder structure, open `.vscode/settings.json` and update the related settings there.
+
+## Dependency Management
+
+The `JAVA PROJECTS` view allows you to manage your dependencies. More details can be found [here](https://github.com/microsoft/vscode-java-dependency#manage-dependencies).

14_Abstract_Class_and_Methods/src/Abstract.java

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+// ? Abstract Method
+// * Method that is declared without an implementation
+
+// ? Abstract Class
+// * Class includes abstract methods
+// * Even one abstract method makes the class abstract
+// * Used to provide a common definition of a base class that multiple derived classes can share
+// Eg: Shape class is a base class for Circle, Rectangle, Triangle, etc.
+
+// Possible to create a reference of an abstract class
+// But cannot create an object of an abstract class
+
+// Abstract Class
+abstractclassParent{
+
+publicParent(){
+System.out.println("I am a constructor of Parent class");
+ }
+
+publicvoidsayHello(){
+System.out.println("Hello");
+ }
+
+// Abstract method
+abstractpublicvoidgreet(); // or public abstract void greet(); --> Preferred
+
+}
+
+classChildextendsParent{
+
+@Override
+publicvoidgreet(){
+System.out.println("Good Morning");
+ }
+
+}
+
+abstractclassChild2extendsParent{
+
+publicvoidth(){
+System.out.println("Good Morning");
+ }
+}
+
+publicclassAbstract{
+publicstaticvoidmain(String[] args){
+
+Parentp = newParent(); // Error because Parent is abstract class
+
+Childc = newChild();
+c.greet(); // Good Morning
+
+Child2c2 = newChild2(); // Error because Child2 is abstract class
+
+ }
+}