Need help with calculating interest

Question

Hey im trying to find out where my calculations are screwing up on the interest is coming up wrong but i am unable to find out where. After every month its suppose to be deposit - withdrawl * monthly interest rate and then add that total to the new month etc... any help will be appreciated. Heres my class and test
public class SavingsAccount
    private double bal;
    private double intRate;
The constructor initializes an object with a
balance and an annual interest rate.
@param bal The account balance.
@param intRate The annual interest rate.
    public SavingsAccount(double bal, double intRate)
    bal= 0.0;
    intRate = 0.0;
    The withdraw method withdraws an amount from
    the account.
    @param amount The amount to withdraw.
    public void withdraw(double amount)
        bal -= amount;
    The deposit method deposits an amount into
    the account.
    @param amount The amount to deposit.
    public void deposit(double amount)
        bal += amount;
    The addInterest method calculates the monthly
    interest and adds it to the account balance.
    public void addInterest()
    // Get the monthly interest rate.
    // Calculate the last amount of interest earned.
    // Add the interest to the balance.
     intRate = bal * (intRate/12);
     bal += intRate;
    The getBalance method returns the account balance.
    @return The account balance.
    public double getBalance()
    return bal;
    The getInterestRate method returns the annual
    interest rate.
    @return The annual interest rate.
    public double getInterestRate()
    return intRate;
    The getLastInterest method returns the last amount
    of interest earned.
    @return The last amount of interest earned.
    public double getLastInterest()
    return bal;
import java.util.Scanner;
import java.text.DecimalFormat;
public class SavingsAccountTest
    public static void main(String args[])
    // Annual interest rate
       double intRate;
    // Starting balance
       double startBal;
    // Amount of deposits for a month
       double deposit;
       double totalDeposit;
    // Amount withdrawn in a month
       double withdrawn;
       double totalWithdrawn;
    // Interest earned
       double intEarned = 0;
    // Deposit accumulator
       deposit = 0.0;
       totalDeposit = 0.0;
    // Withdrawal accumulator
       withdrawn =0.0;
       totalWithdrawn = 0.0;
    // Months that have passed
       double months;
    // Create a Scanner object for keyboard input.
       Scanner keyboard = new Scanner(System.in);
    // Get the starting balance.
       System.out.println("What is your account's starting balance");
       startBal = keyboard.nextDouble();
       while (startBal < 0)
           startBal=0;
    // Get the annual interest rate.
       System.out.println("What is the annual interest rate?");
       intRate = keyboard.nextDouble();
       while (intRate <= 0 )
           intRate = 0;
    // Create a SavingsAccount object.
       SavingsAccount account = new SavingsAccount(0.0, 0.0);
    // Get the number of months that have passed.
       System.out.println("How many months have passed since the " +
                          "account has opened? ");
       months = keyboard.nextDouble();
       while (months <= 0)
           months = 1;
    // Get the deposits and withdrawals for each month.
    for (int i = 1; i <= months; i++)
    // Get the deposits.
       System.out.println("Enter the amount deposited during month " + i);
       deposit= keyboard.nextDouble();
       totalDeposit += deposit;
       while (deposit <=0)
           deposit = 0;
    // Get the withdrawals.
       System.out.println("Enter the amount withdrawn during month " + i);
       withdrawn = keyboard.nextDouble();
       totalWithdrawn += withdrawn;
       while (withdrawn <= 0)
           withdrawn = 0;
    // Add the deposits to the account.
       startBal += deposit;
    // Subtract the withdrawals.
       startBal -= withdrawn;
    // Add the monthly interest.
       intRate = startBal * intRate/12;
       startBal += intRate;
    // Accumulate the amount of interest earned.
       intRate += intEarned;
    // Create a DecimalFormat object for formatting output.
    DecimalFormat dollar = new DecimalFormat("#,##0.00");
    // Display the totals and the balance.
    System.out.println("Total deposited: " + dollar.format(totalDeposit));
    System.out.println("Total withdrawn: " + dollar.format(totalWithdrawn));
    System.out.println("Total interest earned: " + dollar.format(intEarned));
    System.out.println("Account balance: " + dollar.format(startBal));
}

Answer 1

Ok this is what i have fixed up so far but im still having trouble calculating the interest. Problem1) We were given the skeleton to the class and demo. I cannot figure out what to enter in getLastInterest.(completely lost all i need is hint) 2)When i try to get the Total money deposited and i call the account.deposit(balance) it keeps on giving an error void not allowed. Any help is appreciated
public class SavingsAccount
    private double balance;
    private double interest;
    private double intEarned;
    The constructor initializes an object with a
    balance and an annual interest rate.
    @param bal The account balance.
    @param intRate The annual interest rate.
    public SavingsAccount(double bal, double intRate)
    balance = bal;
    interest = intRate;
    The withdraw method withdraws an amount from
    the account.
    @param amount The amount to withdraw.
    public void withdraw(double amount)
        balance -= amount;
    The deposit method deposits an amount into
    the account.
    @param amount The amount to deposit.
    public void deposit(double amount)
        balance += amount;
    The addInterest method calculates the monthly
    interest and adds it to the account balance.
    public void addInterest()
    // Get the monthly interest rate.
    // Calculate the last amount of interest earned.
    // Add the interest to the balance.
     interest = balance * (interest/12);
     interest = intEarned;
     balance += interest;
    The getBalance method returns the account balance.
    @return The account balance.
    public double getBalance()
    return balance;
    The getInterestRate method returns the annual
    interest rate.
    @return The annual interest rate.
    public double getInterestRate()
    return interest;
    The getLastInterest method returns the last amount
    of interest earned.
    @return The last amount of interest earned.
    public double getLastInterest()
    return intEarned;
import java.util.Scanner;
import java.text.DecimalFormat;
public class SavingsAccountTest
    public static void main(String args[])
    // Annual interest rate
       double intRate;
    // Starting balance
       double balance;
    // Amount of deposits for a month
       double deposit;    
    // Amount withdrawn in a month
       double withdraw;
    // Interest earned
       double intEarned = 0;
    // Deposit accumulator
       deposit = 0.0;  
    // Withdrawal accumulator
       withdraw =0.0;    
    // Months that have passed
       double months;
    // Create a Scanner object for keyboard input.
       Scanner keyboard = new Scanner(System.in);
    // Get the starting balance.
       System.out.println("What is your account's starting balance");
       balance = keyboard.nextDouble();
       if (balance < 0)
           balance=0;
    // Get the annual interest rate.
       System.out.println("What is the annual interest rate?");
       intRate = keyboard.nextDouble();
       if (intRate <= 0 )
           intRate = 0;
    // Create a SavingsAccount object. Cannot find Symbol!!
       SavingsAccount account = new SavingsAccount(balance,intRate);
    // Get the number of months that have passed.
       System.out.println("How many months have passed since the " +
                          "account has opened? ");
       months = keyboard.nextDouble();
       if (months <= 0)
           months = 1;
    // Get the deposits and withdrawals for each month.
    for (int i = 1; i <= months; i++)
    // Get the deposits.
       System.out.println("Enter the amount deposited during month " + i);
       deposit= keyboard.nextDouble();
       account.deposit(deposit);
       if (deposit <=0)
           deposit = 0;
    // Get the withdrawals.
       System.out.println("Enter the amount withdrawn during month " + i);
       withdraw = keyboard.nextDouble();
       account.withdraw(withdraw);
       if (withdraw <= 0 || withdraw >= balance)
           withdraw = 0;
    // Add the deposits to the account.
       account.deposit(balance);
    // Subtract the withdrawals.
       account.withdraw(balance);
    // Add the monthly interest.
       account.addInterest();
    // Accumulate the amount of interest earned. ????? Wrong
       intRate += intEarned;
    // Create a DecimalFormat object for formatting output.
    DecimalFormat dollar = new DecimalFormat("#,##0.00");
    // Display the totals and the balance.
    System.out.println("Total deposited: " + dollar.format(account.deposit(balance)));
    System.out.println("Total withdrawn: " + dollar.format(account.withdraw(balance)));
    System.out.println("Total interest earned: " + dollar.format(account.addInterest()));
    System.out.println("Account balance: " + dollar.format(account.getBalance()));
}