자바 saving account 를 공부하고있는데 class method 에서 막히네요

import java.text.DecimalFormat;
 
import javax.swing.JOptionPane;
 
 
public class SavingAccount {
 
	public static void main(String[] args) {
 
		String intRate, stBalance, psMonth, input;
		double interRate, startBalance, depositIn, monthWith;
		int passMonth;
 
		DecimalFormat dollar = new DecimalFormat("##0.00");
 
		intRate = JOptionPane.showInputDialog("Enter the annual interest rate.");
		interRate = Double.parseDouble(intRate);
 
		stBalance = JOptionPane.showInputDialog("Enter the starting balance.");
		startBalance = Double.parseDouble(stBalance);
 
		SAccount sAccount = new SAccount(startBalance, interRate);
 
		psMonth = JOptionPane.showInputDialog("Enter the number of months that have passed since the account was established.");
		passMonth = Integer.parseInt(psMonth);
 
		for(int i = passMonth; i < 12; i++){
 
			input = JOptionPane.showInputDialog("Input the amount of money you want to deposit.");
			depositIn = Double.parseDouble(input);
			sAccount.setDeposit(depositIn);
 
			input = JOptionPane.showInputDialog("Input the amount of money you want to withdraw.");
			monthWith = Double.parseDouble(input);
			sAccount.setWithdrawal(monthWith);
			sAccount.setTotalInt(interRate);
		}JOptionPane.showMessageDialog(null, "total ending balance : " + dollar.format(sAccount.getBalance()) +
				"\ntotal amount of deposit : " + dollar.format(sAccount.getDeposit()) + 
				"\ntotal amount of withdral : " + dollar.format(sAccount.getwithdral()) +
				"\ntotal interest you earned : " + dollar.format(sAccount.getTotalInt()));
		System.exit(0);
	}
}

public class SAccount {
 
	private double interestRate, interest;
	private double balance;
	private double deposit;
	private double withdral;
 
 
	public SAccount(double bal,double intRate){
		balance = bal;
		interestRate = intRate;
	}
 
	public void setDeposit(double dposit){
		deposit += dposit;
	}
 
	public void setWithdrawal(double withd){
		withdral -= withd;
	}
 
	public void setIntRate(double rate){
		interestRate = rate;
	}
 
	public void setBalance(double bal){
		balance = bal;
		balance = deposit - withdral;	
		balance += balance;
	}
 
	public void setTotalInt(double intRate){
		interestRate = intRate; 
		interest = (interestRate / 12) * balance;
	}
 
	public double getDeposit(){
		return deposit;
	}
 
	public double getwithdral(){
		return withdral;
	}
 
	public double getBalance(){
		return balance;
	}
 
	public double getTotalInt(){
		return interest;
	}
}