Write a Java program to demonstrate OOP Inheritance — single, multilevel, and hierarchical.

// Parent class
class Animal {
    String name;

    void eat() {
        System.out.println(name + " eats food");
    }

    void breathe() {
        System.out.println(name + " breathes air");
    }
}

// Child class inherits from Animal
class Dog extends Animal {
    void bark() {
        System.out.println(name + " barks: Woof!");
    }
}

public class SingleInheritance {
    public static void main(String[] args) {
        Dog dog = new Dog();
        dog.name = "Buddy";

        dog.eat();     // inherited from Animal
        dog.breathe(); // inherited from Animal
        dog.bark();    // Dog's own method
    }
}

Buddy eats food
Buddy breathes air
Buddy barks: Woof!

class Vehicle {
    void start() { System.out.println("Vehicle started"); }
}

class Car extends Vehicle {
    void drive() { System.out.println("Car is driving"); }
}

class ElectricCar extends Car {
    void charge() { System.out.println("Electric car is charging"); }
}

public class MultilevelInheritance {
    public static void main(String[] args) {
        ElectricCar tesla = new ElectricCar();
        tesla.start();   // from Vehicle (grandparent)
        tesla.drive();   // from Car (parent)
        tesla.charge();  // own method
    }
}

Vehicle started
Car is driving
Electric car is charging

class WebDriver {
    void open(String url) { System.out.println("Opening: " + url); }
    void close() { System.out.println("Browser closed"); }
}

class ChromeDriver extends WebDriver {
    void launchChrome() { System.out.println("Chrome launched"); }
}

class FirefoxDriver extends WebDriver {
    void launchFirefox() { System.out.println("Firefox launched"); }
}

public class HierarchicalInheritance {
    public static void main(String[] args) {
        ChromeDriver chrome = new ChromeDriver();
        chrome.launchChrome();           // own
        chrome.open("https://google.com"); // inherited

        FirefoxDriver firefox = new FirefoxDriver();
        firefox.launchFirefox();         // own
        firefox.close();                 // inherited
    }
}

class Parent {
    String name = "Parent";
    void display() { System.out.println("Parent class"); }
}

class Child extends Parent {
    String name = "Child";

    void display() {
        super.display();           // call parent method
        System.out.println("Child class");
        System.out.println("Parent name: " + super.name);  // parent field
        System.out.println("Child name: " + this.name);    // child field
    }
}

// This causes compile error:
// class C extends A, B {}  // ERROR: multiple inheritance not allowed

// Use interfaces instead:
interface A { void methodA(); }
interface B { void methodB(); }
class C implements A, B {
    public void methodA() { System.out.println("A"); }
    public void methodB() { System.out.println("B"); }
}