First.java

import java.util.Scanner;

class Human{
    int age;
    String name;

    public void sayAboutSelf(){
        System.out.println("My name is " + this.name + ". I am " + this.age + " years old.");
    }
}

class First {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Human h1 = new Human();

        System.out.print("Enter name of new human: ");
        h1.name = sc.nextLine();
        System.out.print("And age:");
        h1.age = sc.nextInt();

        h1.sayAboutSelf();

    }
}

Polymorphism.java

class Duck{
    public void quack(){
        System.out.println("quack");
    }
}

class FirstDuck extends Duck{
    public void quack(){
        System.out.println("quack-quack-kryaaaa!!!");
    }
}

class SecondDuck extends Duck{
    public void quack(){
        System.out.println("I can't quack!");
    }
}


class Polymorphism {
    public static void ducksWantQuack(Duck[] d){
        for (int i = 0; i < d.length; i++) {
            d[i].quack();
        }
    }

    public static void main(String[] args) {
        Duck d1 = new Duck();
        FirstDuck d2 = new FirstDuck();
        SecondDuck d3 = new SecondDuck();

        Duck[] ducks = new Duck[4];

        ducks[0] = d1;
        ducks[1] = d2;
        ducks[2] = d3;
        ducks[3] = new FirstDuck();

        ducksWantQuack(ducks);
    }
}

Second.java

class Human {
    int age;
    String name;

    public void sayAboutSelf(){
        System.out.println("My name is " + this.name + ". I am " + this.age + " years old.");
    }
}

class Telephone {
    String model;
    String brand;
    String number;

    public void showInfo(){
        System.out.println("Model: " + this.model);
        System.out.println("Brand: " + this.brand);
        System.out.println("Number: " + this.number);
    }
}

class ModernHuman extends Human {
    Telephone tel;

    public void sayAboutSelf(){
        super.sayAboutSelf();//Виклик метода з батьківського класу

        System.out.println("And i have this phone:");
        this.tel.showInfo();
    }

}

class Main {
    public static void main(String[] args) {
        ModernHuman h1 = new ModernHuman();

        h1.name = "Sasha";
        h1.age = 19;

        h1.tel = new Telephone();
        h1.tel.brand = "Sony";
        h1.tel.model = "ST21i2";
        h1.tel.number = "+380930380763";

        h1.sayAboutSelf();

    }
}