Week 6 of OOP in JAVA

Write a Java program using an interface Shape that declares a method area(). Implement the interface in two classes Circle and Rectangle to calculate their respective areas.

interface Shape{
    void area();
}

class Circle implements Shape{
    double radius;

    Circle(double r){
        radius = r;
    }

    public void area(){
        double a = 3.14 * radius * radius;
        System.out.println("Area of Circle = " + a);
    }
}

class Rectangle implements Shape{
    double length, breadth;

    Rectangle(double l, double b){
        length = l;
        breadth = b;
    }

    public void area(){
        double a = length * breadth;
        System.out.println("Area of Rectangle = " + a);
    }
}

public class ShapeInterfaceDemo{
    public static void main(String[] args){
        Circle c = new Circle(5);
        Rectangle r = new Rectangle(4,6);

        c.area();
        r.area();
    }
}

Write a Java program where two interfaces InternalMarks and ExternalMarks declare methods for accepting marks. A class Result implements both interfaces and calculates the total marks.

interface InternalMarks{
    void setInternal(int m);
}

interface ExternalMarks{
    void setExternal(int m);
}

class Result implements InternalMarks, ExternalMarks{
    int internal, external;

    public void setInternal(int m){
        internal = m;
    }

    public void setExternal(int m){
        external = m;
    }

    void total(){
        System.out.println("Internal Marks = " + internal);
        System.out.println("External Marks = " + external);
        System.out.println("Total Marks = " + (internal + external));
    }
}

public class ResultDemo{
    public static void main(String[] args){
        Result r = new Result();

        r.setInternal(40);
        r.setExternal(55);

        r.total();
    }
}

Write a Java program using an interface Bank that contains methods deposit() and withdraw(). Implement this interface in a class Account to simulate basic banking operations.

import java.util.Scanner;

interface Bank{
    void deposit(double amount);
    void withdraw(double amount);
}

class Account implements Bank{
    double balance = 0;

    public void deposit(double amount){
        balance += amount;
        System.out.println("Deposited: " + amount);
        System.out.println("Balance: " + balance);
    }

    public void withdraw(double amount){
        if(amount > balance){
            System.out.println("Insufficient balance");
        }
        else{
            balance -= amount;
            System.out.println("Withdrawn: " + amount);
            System.out.println("Balance: " + balance);
        }
    }
}

public class BankDemo{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        Account acc = new Account();

        System.out.print("Enter deposit amount: ");
        double d = sc.nextDouble();
        acc.deposit(d);

        System.out.print("Enter withdraw amount: ");
        double w = sc.nextDouble();
        acc.withdraw(w);
    }
}