روز 2 جاوا اوه ، برنامه نمونه

class Car {
    String brand;
    int speed;

    void display() {
        System.out.println("Brand: " + brand + ", Speed: " + speed);
    }
}

public class Main {
    public static void main(String[] args) {
        Car myCar = new Car(); // Creating an object
        myCar.brand = "Toyota";
        myCar.speed = 120;
        myCar.display();
    }
}

class BankAccount {
    private double balance;

    public void deposit(double amount) {
        balance += amount;
    }

    public double getBalance() {
        return balance;
    }
}

class Animal {
    void eat() {
        System.out.println("This animal eats food.");
    }
}

class Dog extends Animal {
    void bark() {
        System.out.println("Dog barks");
    }
}

public class Main {
    public static void main(String[] args) {
        Dog myDog = new Dog();
        myDog.eat();  // Inherited from Animal
        myDog.bark(); // Defined in Dog
    }
}

class MathOperations {
    int add(int a, int b) {
        return a + b;
    }

    double add(double a, double b) {
        return a + b;
    }
}

class Parent {
    void show() {
        System.out.println("Parent's show method");
    }
}

class Child extends Parent {
    @Override
    void show() {
        System.out.println("Child's show method");
    }
}

abstract class Vehicle {
    abstract void start(); // Abstract method
}

class Bike extends Vehicle {
    void start() {
        System.out.println("Bike is starting...");
    }
}

interface Animal {
    void makeSound(); // Abstract method
}

class Cat implements Animal {
    public void makeSound() {
        System.out.println("Meow!");
    }
}

public class HelloWorld {  // Class name does not match the filename
    public static void main(String[] args) {
        System.out.println("Hello, Java!");
    }
}

public class Hello {
    // No main method
}

public class Hello {
    public static void main(String[] args) {
        System.out.println("Hello, Java!");
    }
}

public class Hello {
    void main() {  // Missing 'public static' and incorrect parameters
        System.out.println("Hello, Java!");
    }
}

public class Hello {
    public static void main(String[] args) {
        System.out.println("Hello, Java!");
    }
}

public class Hello {
    public static void main(String[] args) {
        System.out.println("Hello, Java!")  // Missing semicolon
    }
}

public class Hello {
    public static void main(String[] args) {
        System.out.println("Hello, Java!");
    }
}

javac Hello.java  # Compile
java Hello        # Run (without .class or .java)

java Hello.java  # ❌ Wrong

Error: Could not find or load main class Hello.java