java-core-practice/OOPs at main · Amrutha-space/java-core-practice · GitHub

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### Encapsulation

class BankAccount {

    private double balance;
    public void deposit(double amount) {
        if (amount > 0) {
            balance += amount;
        }
    }
    public double getBalance() {
        return balance;
    }
}

### inheritance

class Vehicle {
    int speed = 60;

    void move() {
        System.out.println("Vehicle is moving");
    }
}

class Car extends Vehicle {
    void fuel() {
        System.out.println("Car uses petrol");
    }
}

class Demo {
    public static void main(String[] args) {
        Car c = new Car();
        c.move();
        c.fuel();
        System.out.println(c.speed);
    }
}

###polymorphism

class Payment {
    void pay() {
        System.out.println("Payment method");
    }
}

class UPI extends Payment {
    void pay() {
        System.out.println("Paying using UPI");
    }
}

class Card extends Payment {
    void pay() {
        System.out.println("Paying using Card");
    }
}

class Demo {
    public static void main(String[] args) {

        Payment p;

        p = new UPI();
        p.pay();

        p = new Card();
        p.pay();
    }
}

#### abstraction

class UPI implements Payment {
    public void pay() {
        System.out.println("Paying via UPI");
    }
}

class Card implements Payment {
    public void pay() {
        System.out.println("Paying via Card");
    }
}