exercise 3.4

public class BankAccount {

    public static void main(String[] args) {}
        private double balance;

        public BankAccount()
        {
        balance = 0;
        }
        public BankAccount(double initialBalance)
        {
        balance = initialBalance;
        }
        public void deposit(double amount)
        {
        double newBalance = balance + amount;
        balance = newBalance;
        }
        public void withdraw(double amount)
        {
        double newBalance = balance - amount;
        balance = newBalance;
        }
        public double getBalance()
        {
        return balance;
        }
        public double addInterest(double rate)
        {
        balance = balance * rate + balance;
        return balance;
        }
        }


public class BankAccountTester
{
public static void main(String[] args)
{
BankAccount momsSavings = new BankAccount(1000);
System.out.println("old Balance: " +momsSavings.getBalance());// getBalance
momsSavings.addInterest(.1);

System.out.println("new Balance: " +momsSavings.getBalance());// getBalance
System.out.println(momsSavings);
System.out.println("Expected:1120");
}
}