Class Variables and Methods Practice Test

How does the static method interact with the class variable in this code?

// BankAccount demonstrates class variables (static) and class methods (static).

public class BankAccount {

    // Class variable shared by all accounts in the bank.

    private static double bankTotalBalance = 0.0;

    // Instance variable unique to each BankAccount object.

    private double accountBalance;

    // Constructor initializes an account with an opening deposit.

    public BankAccount(double openingDeposit) {

        accountBalance = openingDeposit;

        // Update the class-level total whenever an account is created.

        bankTotalBalance += openingDeposit;

    }

    // Static (class) method returns the total balance across all accounts.

    public static double getBankTotalBalance() {

        return bankTotalBalance;

    }

    // Instance method deposits money into this account and updates the class total.

    public void deposit(double amount) {

        accountBalance += amount;

        bankTotalBalance += amount;

    }

    // Instance method withdraws money from this account and updates the class total.

    public void withdraw(double amount) {

        accountBalance -= amount;

        bankTotalBalance -= amount;

    }

    // Main method demonstrates creating accounts and adjusting balances.

    public static void main(String[] args) {

        BankAccount a = new BankAccount(100.0);

        BankAccount b = new BankAccount(50.0);

        a.deposit(25.0);

        b.withdraw(10.0);

        System.out.println(BankAccount.getBankTotalBalance());

    }

}

What will be the output when the main method is executed?

// Student demonstrates class variables (static) and class methods (static).

public class Student {

    // Class variable tracking total enrolled students across all instances.

    private static int totalEnrolled = 0;

    // Instance variable indicating whether this student is currently enrolled.

    private boolean enrolled;

    // Constructor enrolls the student upon creation.

    public Student() {

        enrolled = true;

        totalEnrolled++;

    }

    // Instance method withdraws this student and updates the class total.

    public void withdraw() {

        if (enrolled) {

            enrolled = false;

            totalEnrolled--;

        }

    }

    // Static method returns total enrolled students.

    public static int getTotalEnrolled() {

        return totalEnrolled;

    }

    // Main method simulates enrollment and withdrawal.

    public static void main(String[] args) {

        Student s1 = new Student();

        Student s2 = new Student();

        s1.withdraw();

        Student s3 = new Student();

        System.out.println(Student.getTotalEnrolled());

    }

}