Variable

public class Variables {
    public static void main(String[] args) {
        // examples of Java variables
        int age = 18;     // valid and good practice
        int AGE = 20;     // valid and good practice
        int myAge = 22;   // valid and good practice
        int my_age = 21;  // valid and good practice
        int _age = 25;    // valid but bad practice
        int $age = 32;    // valid but bad practice
        int 1age = 19;    // invalid variable
        int my age = 23;  // invalid variable

        byte itemQuantity = 5;
        byte batteryLevel = 85;
        short numOfSmartphones = 350;
        short numOfTablets = 125;
        int userAge = 28;
        int accountNumber = 123456;
        int x = 5;
        int y = 6;
        System.out.println(x + y);

        int myNum = 15;
        myNum = 20;
        System.out.println(myNum);

        int x1 = 12, y1 = 15, z1 = 17;
        System.out.println(x1 + y1 + z1);

        int x2, y2, z2;
        x2 = y2 = z2 = 35;
        System.out.println(x2 + y2 + z2);

        int totalStudents = 30;  // Number of students in the course
        System.out.println("Total number of students: " + totalStudents);

        long creditCardNumber = 1234_5678_9012_3456L;
        long worldPopulation = 7_900_000_000L;
        long population = 1393409038L;  // Population of India (in billions)
        System.out.println("Population of India: " + population);

        double accountBalance = 5000.50;
        double personHeight = 1.75;
        float temperatureCelsius = 37.5f;
        double averageScore = 85.7;  // Average score of the student
        System.out.println("Student's average score: " + averageScore);

        float itemPrice = 19.99f;  // Price of the item
        float totalPrice = itemPrice * 1.1f;  // Total price with tax (10%)
        System.out.println("Total price with tax: " + totalPrice);

        boolean isLoggedIn = true;  // Status of user login
        boolean isActiveAccount = true;
        boolean isSubscribed = true;

        char initialLetter = 'J';
        char grade = 'A';  // Student's grade
        System.out.println("Student's grade: " + grade);

        String userEmail = "alice.johnson@example.com";
        String studentName = "John Doe";  // Student's name
        System.out.println("Student's name: " + studentName);
        String myString = "Java Programming Language";

        double TAX_RATE = 0.08;  // Constant tax rate of 8%
        double price = 100.0;
        double tax = price * TAX_RATE;
        double total = price + tax;
        System.out.println("Total price with tax: " + total);

        // approximate light speed in miles per second
        int lightSpeed = 186000;
        long days = 1000;
        long seconds;
        long distance;
        seconds = days * 24 * 60 * 60; // convert to seconds
        distance = lightSpeed * seconds; // compute distance
        System.out.println("In " + days);
        System.out.println(" days light will travel about ");
        System.out.println(distance + " miles");

    }
}