Java: How to pause the output after a certain number of iterations until a key is pressed

Question

I'm learning Java for one of my college courses, and I need to know how to pause the output of my program after every 12 iterations of a for loop. I have a loop that iterates 360 times, and I'd like for every 12 items the loop outputs the output to stop until a key is pressed. I have done quite a bit of searching, but everything I've found was in a much more advanced context and I didn't quite understand what else was going on in the code. There is no GUI for this program, and it is so simple that I could just paste all of the code here:

public class MyMain

{      
    static double principal = 200000.00;
    static double interest = .0575;
    static int term = 360;
    static DecimalFormat currency = new DecimalFormat("###,###.##");

    public static void main(String[] args)
    {

        MortgageCalculator mortgageWeek2 = new MortgageCalculator(principal, interest, term);
        double monthlyPayment = mortgageWeek2.calculate();
        System.out.println("Welcome to my Mortgage Calculator.");
        System.out.println("The principal on this loan is $" + currency.format(principal) + ".");
        System.out.println("The interest on this loan is " + (interest * 100) + "%.");
        System.out.println("The term on this loan is " + term + " months (" + term / 12 + " years).");
        System.out.println("Payments on this loan will be $" + currency.format(monthlyPayment));

        double balanceRemaining = 200000.0;



        for (int i = 0; i < 30 * 12; i++)
        {
            double interestPaid = balanceRemaining * .0575 / 12;
            double principalPaid = monthlyPayment - interestPaid;
            balanceRemaining = balanceRemaining - principalPaid;
            System.out.println("Month " + (i + 1) + " \tPayment Amount: $" + currency.format(monthlyPayment) + 
                    "\tInterest Paid: $" + currency.format(interestPaid) + 
                    " \tPrincipal Paid: $" + currency.format(principalPaid) + 
                    "    \tBalance Remaining: $" + currency.format(balanceRemaining));
        }
      }
    }

Answer 1

Break your for loop in two segments and add a input statement in the outer loop as below:

    Scanner input = new Scanner(System.in);
    String userInput = null;
    for (int i = 0; i < 30; i++)
    {
      for (int j = 0; j < 12; j++)
      {
        double interestPaid = balanceRemaining * .0575 / 12;
        double principalPaid = monthlyPayment - interestPaid;
        balanceRemaining = balanceRemaining - principalPaid;
        System.out.println("Month " + (i*12+j + 1) + 
                 " \tPayment Amount: $" + currency.format(monthlyPayment) + 
                "\tInterest Paid: $" + currency.format(interestPaid) + 
                " \tPrincipal Paid: $" + currency.format(principalPaid) + 
                "    \tBalance Remaining: $" + currency.format(balanceRemaining));
      }
      userInput = input.nextLine();
    }
    input.close();

Once it stops, you need to press any character and a return key or just the return key.

Answer 2

The best way to do this is to make an inner loop that does the printing (has 12 iterations) and wrap that with a loop that waits for input. So you have

Scanner input = new Scanner(System.in);
String in = null;  


for (int j = 0; j < 30; j++) {
      for (int i = 0; i < 12; i++)
      {
        double interestPaid = balanceRemaining * .0575 / 12;
        double principalPaid = monthlyPayment - interestPaid;
        balanceRemaining = balanceRemaining - principalPaid;
        System.out.println("Month " + (i + 1) + " \tPayment Amount: $" + currency.format(monthlyPayment) + 
                "\tInterest Paid: $" + currency.format(interestPaid) + 
                " \tPrincipal Paid: $" + currency.format(principalPaid) + 
                "    \tBalance Remaining: $" + currency.format(balanceRemaining));
    }

    System.out.println("Press any key.");
    in = input.next();

 }
 input.Close();

Answer 3

You can user "KeyPress" event to check weather a key is press or not.You can also find out which key is pressed Then you "break" to stop loop iteration...Hope this help

Here is an example

public void keyPressed(KeyEvent e) {
    int keyCode = e.getKeyCode();
    switch( keyCode ) { 
        case KeyEvent.VK_UP:
            // handle up 
            break;
        case KeyEvent.VK_DOWN:
            // handle down 
            break;
        case KeyEvent.VK_LEFT:
            // handle left
            break;
        case KeyEvent.VK_RIGHT :
            // handle right
            break;
     }
} 

you can get keycode of any key from internet easily.

Answer 4

You just need to use System.in.read(); to read user input. Cheers!