#java #javatutorial #javacourse public class Main { public static void main(String[] args) { // abstract = Used to define abstract classes and methods. // Abstraction is the process of hiding implementation details // and showing only the essential features. // Abstract classes CAN'T be instantiated directly. // Can contain 'abstract' methods (which must be implemented) // Can contain 'concrete' methods (which are inherited) Circle circle = new Circle(3); Triangle triangle = new Triangle(4, 5); Rectangle rectangle = new Rectangle(6, 7); (); (); (); ( ()); ( ()); ( ()); } } public abstract class Shape { abstract double area(); // ABSTRACT void display(){ // CONCRETE ("This is a shape"); } } public class Circle extends Shape{ double radius; Circle(double radius){ = radius; } @Override double area(){ return * radius * radius; } } public class Triangle extends Shape{ double base; double height; Triangle(double base, double height){ = base; = height; } @Override double area(){ return 0.5 * base * height; } } public class Rectangle extends Shape{ double length; double width; Rectangle(double length, double width){ = length; = width; } @Override double area(){ return length * width; } }