Take user input and store to array in a file

Question

I am trying to store multiple user inputs as a byte based file and then take the files numbers and use them for calculation in the program I have written. I started by converting the string to a double, but the I ran into the issue of reading the values and subbing in the the calc methods. I figured out that I am suppose to use fileOutputStream but have no idea how to incorporate into the code. Any guidance would be appreciated. Please see code for reference:

import java.util.Scanner;
import java.io.*;

public class BankApp {
    public static void main (String [] args) throws IOException{

        double cash = 0;
        int years = 0;
        double pv = 0;
        String line = null;

        String filename = "bank.txt";

        Scanner in = new Scanner(System.in);

        System.out.println("How much money would you like to have?");
        cash = in.nextDouble();

        System.out.println("How many years is your investment?");
        years = in.nextInt();

        Bank1 bank1 = new Bank1(cash, years);

        BufferedWriter bw = new BufferedWriter(new FileWriter(filename));       
        bw.write(String.valueOf(cash));
        bw.close();

        BufferedReader br = new BufferedReader(new FileReader(filename));       
        while((line = br.readLine()) != null)
        {
            //System.out.println(line);
        }

        System.out.println("The present value to invest over the years to reach goal: $"+bank1.presentValue());
        System.out.println("The furture value in the account will be: $"+bank1.futureValue());
    }
}

Here is the second class that does all the calculations.

public class Bank1 {

    private double cash;
    private double rate = .0425;
    private int years;

    public Bank1(double cash, int years){
        this.cash = cash;
        this.years = years;     
    }n

    public double presentValue(){
        double pv = cash/Math.pow((1+rate), years);
        double present = Math.round(pv *100);
        present = present/100;
        return present;
    }


    public double  futureValue(){
        double fv = this.presentValue()*Math.pow((1+rate), years);
        double future = Math.round(fv *100);
        future = future/100;
        return future;
    }

}

Answer 1

Your best option is to read up on the different types of Character / Byte streams in the java documentation, I usually go there every time I read/write data to find one that suits my need.

http://docs.oracle.com/javase/7/docs/api/java/io/package-summary.html

(This is the documentation for the java.io package in your code you say import java.io.* that gives you access to anything listed in the documentation)

When you say "I figured out that I am suppose to use fileOutputStream but have no idea how to incorporate into the code." you don't HAVE to unless this a assignment that requires it, I would use a FileWriter or ObjectOutputStream. ObjectOutputStream would be perfect for what you are trying to do.