AP Computer Science a Flashcards: Class Variables And Methods

// 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());
    }
}