Method overriding

class Animal {
    String sound() {
        return "...";
    }
}

class Cow extends Animal {
    @Override
    String sound() {
        return "Moo";
    }
}

class Cat extends Animal {
    @Override
    String sound() {
        return "Meow";
    }
}

public class Main {
    public static void main(String[] args) {
        Animal[] animals = { new Animal(), new Cow(), new Cat() };
        for (Animal a : animals) {
            System.out.println(a.getClass().getSimpleName() + ": " + a.sound());
        }
    }
}

class Book {
    private final String title;
    private final double price;

    Book(String title, double price) {
        this.title = title;
        this.price = price;
    }

    @Override
    public String toString() {
        return title + " (Rs " + price + ")";
    }
}

public class Main {
    public static void main(String[] args) {
        Book b = new Book("Wings of Fire", 299);
        System.out.println(b);
        System.out.println("In cart: " + b);
    }
}

class Report {
    String header() {
        return "Shree Traders";
    }
}

class SalesReport extends Report {
    @Override
    String header() {
        return super.header() + " - Sales";
    }
}

public class Main {
    public static void main(String[] args) {
        Report r = new SalesReport();
        System.out.println(r.header());
        System.out.println(new Report().header());
    }
}

class Shape {
    Shape copy() {
        return new Shape();
    }
}

class Circle extends Shape {
    double radius;

    Circle(double radius) {
        this.radius = radius;
    }

    @Override
    Circle copy() {
        return new Circle(radius);
    }
}

public class Main {
    public static void main(String[] args) {
        Circle c = new Circle(7);
        Circle c2 = c.copy();
        c2.radius = 10;
        System.out.println("original " + c.radius + ", copy " + c2.radius);
    }
}

class Vehicle {
    static String category() { return "Vehicle"; }
    int maxSpeed() { return 100; }
}

class Bus extends Vehicle {
    static String category() { return "Bus"; }

    @Override
    int maxSpeed() { return 80; }
}

public class Main {
    public static void main(String[] args) {
        Vehicle v = new Bus();
        Bus b = new Bus();
        System.out.println("v: " + v.category() + ", " + v.maxSpeed());
        System.out.println("b: " + b.category() + ", " + b.maxSpeed());
    }
}

class Sensor {
    protected double read() {
        return 0;
    }
}

class TemperatureSensor extends Sensor {
    @Override
    public double read() {
        return 31.5;
    }
}

public class Main {
    public static void main(String[] args) {
        TemperatureSensor t = new TemperatureSensor();
        System.out.println("Temperature: " + t.read() + " C");
        Sensor s = t;
        System.out.println("Via Sensor: " + s.read());
    }
}

import java.util.HashSet;
import java.util.Set;

class Customer {
    private final String mobile;

    Customer(String mobile) {
        this.mobile = mobile;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (!(o instanceof Customer)) return false;
        Customer other = (Customer) o;
        return mobile.equals(other.mobile);
    }

    @Override
    public int hashCode() {
        return mobile.hashCode();
    }
}

public class Main {
    public static void main(String[] args) {
        Set<Customer> set = new HashSet<>();
        set.add(new Customer("98200 12345"));
        set.add(new Customer("98200 12345"));
        System.out.println("Customers in set: " + set.size());
    }
}

class Shape {
    double area() {
        return 0;
    }

    String name() {
        return getClass().getSimpleName();
    }
}

class Rect extends Shape {
    private final double w, h;
    Rect(double w, double h) { this.w = w; this.h = h; }

    @Override
    double area() { return w * h; }
}

class Circle extends Shape {
    private final double r;
    Circle(double r) { this.r = r; }

    @Override
    double area() { return Math.PI * r * r; }
}

class Triangle extends Shape {
    private final double base, height;
    Triangle(double base, double height) { this.base = base; this.height = height; }

    @Override
    double area() { return 0.5 * base * height; }
}

public class Main {
    public static void main(String[] args) {
        Shape[] canvas = { new Rect(40, 25), new Circle(10), new Triangle(30, 12) };
        double total = 0;
        for (Shape s : canvas) {
            System.out.printf("%-8s %8.2f sq cm%n", s.name(), s.area());
            total += s.area();
        }
        System.out.printf("Total    %8.2f sq cm%n", total);
    }
}

class Employee {
    protected final String name;
    protected final double basic;

    Employee(String name, double basic) {
        this.name = name;
        this.basic = basic;
    }

    double bonus() {
        return Math.round(basic * 0.0833);
    }
}

class Manager extends Employee {
    Manager(String name, double basic) { super(name, basic); }

    @Override
    double bonus() {
        return super.bonus() + 10000;
    }
}

class Intern extends Employee {
    Intern(String name, double basic) { super(name, basic); }

    @Override
    double bonus() {
        return 3000;
    }
}

public class Main {
    public static void main(String[] args) {
        Employee[] staff = {
            new Employee("Anil", 30000), new Manager("Kiran", 70000), new Intern("Zoya", 15000)
        };
        double total = 0;
        for (Employee e : staff) {
            System.out.println(e.name + " (" + e.getClass().getSimpleName() + "): Rs " + e.bonus());
            total += e.bonus();
        }
        System.out.println("Total bonus payout: Rs " + total);
    }
}

class DeliveryVehicle {
    int eta(double km) {
        return (int) Math.ceil(km / 30 * 60) + 10;
    }
}

class Bike extends DeliveryVehicle {
    @Override
    int eta(double km) {
        return (int) Math.ceil(km / 40 * 60) + 10;
    }
}

class Drone extends DeliveryVehicle {
    @Override
    int eta(double km) {
        if (km > 10) return -1;
        return (int) Math.ceil(km / 60 * 60) + 2;
    }
}

public class Main {
    public static void main(String[] args) {
        DeliveryVehicle[] fleet = { new DeliveryVehicle(), new Bike(), new Drone() };
        double[] trips = {6, 15};
        for (double km : trips) {
            System.out.print(km + " km:");
            for (DeliveryVehicle v : fleet) {
                int m = v.eta(km);
                System.out.print("  " + v.getClass().getSimpleName() + "=" + (m < 0 ? "n/a" : m + " min"));
            }
            System.out.println();
        }
    }
}