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Thread: How to round to 2 decimal places in a dialog box

  1. #1
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    Default How to round to 2 decimal places in a dialog box

    I know how to print using the printf method, but can't for the life of me get it to round to two decimal places using a dialog box.

    import javax.swing.JOptionPane;
     
    public class Program6 {
     
        public static void main(String[] args) {
            //declare variables
            double loanAmount, annualInterestRate, monthlyPayment, 
            monthlyInterestRate, monthlyInterest, totalPaid;
     
            int month;
     
     
    //promt user to enter amount borrowed
            String loanAmountString = JOptionPane.showInputDialog
                    (null, "Enter the amount to be borrowed in dollars");
            loanAmount = Double.parseDouble(loanAmountString);
     
            //prompt user to enter annual interest
            String annualInterestRateString = JOptionPane.showInputDialog 
                    (null, "Enter the annual interest rate, eg 12 percent");
            annualInterestRate = Double.parseDouble(annualInterestRateString);
            annualInterestRate = (annualInterestRate / 100);
     
           //calculate monthly interest rate
            monthlyInterestRate = annualInterestRate / 12;
     
            //calculate monthly interest payment
            monthlyInterest = loanAmount * monthlyInterestRate;
     
            //display monthly interest
            JOptionPane.showMessageDialog(null, "The Monthly interest is " +
                    monthlyInterest);
     
            //promt user to enter amount to be paid each month
            String monthlyPaymentString = JOptionPane.showInputDialog
                    (null, "Enter the amount to be paid each month. "
                    + "Amount must be greater than monthly interest.");
            monthlyPayment = Double.parseDouble(monthlyPaymentString);
     
     
     
            //parse double
            totalPaid = 0.00f;
            month = 0;
     
            //begin first loop
            while (monthlyPayment <= monthlyInterest) {
          String newMonthlyPaymentString = JOptionPane.showInputDialog
          (null, "Your payment does not cover the interest on your loan. "
                  + "Please enter a larger amount for your monthly payment.");
          monthlyPayment = Double.parseDouble(newMonthlyPaymentString);
            }
     
            double loanAmountRemaining = loanAmount;
     
            //begin second loop
            while (loanAmount != 0) {
     
            totalPaid += monthlyPayment;
     
            monthlyInterest = loanAmountRemaining * monthlyInterestRate;
     
            loanAmount += monthlyInterest;
     
            loanAmountRemaining = (loanAmount - totalPaid);
     
            month++;
     
            if (monthlyPayment > (loanAmountRemaining))
            {
                totalPaid += loanAmountRemaining;
     
                loanAmount = 0;
     
                month++;
            }
            }
     
            //display message that loan has been paid
            String.format("%.2f", totalPaid);
            JOptionPane.showMessageDialog
    (null,"Congradulations! You have paid off your loan. Total amount paid is $" 
                    + totalPaid);
    }
    }

    //display message that loan has been paid
    String.format("%.2f", totalPaid);
    JOptionPane.showMessageDialog
    (null,"Congradulations! You have paid off your loan. Total amount paid is $"
    + totalPaid);
    }
    }
    The last part is the part i want limited to 2 decimal places.


  2. #2
    Super Moderator pbrockway2's Avatar
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    Default Re: How to round to 2 decimal places in a dialog box

    You aren't doing anything with the String returned by String.format("%.2f", totalPaid). Use it in the message you display.

    (Notice that String.format() does return something. It does not alter totalPaid in any way.)

  3. #3
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    Default Re: How to round to 2 decimal places in a dialog box

    Try this :

    Math.round(number*100.0)/100.0;

    And also check this link:
    java - How to round the double value to 2 decimal points? - Stack Overflow
    Regards
    Android developer
    Trinay Technology Solutions
    http://www.trinaytech.com
    5705750475

  4. #4
    Member Zyrion's Avatar
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    Default Re: How to round to 2 decimal places in a dialog box

    You can use the DecimalFormat class to format your number.

    Line 3: Create an instance of your object and give it the parameters particular to your needs.
    Line 6. Call the method for formatting, which then produces a string expression.
    import java.text.DecimalFormat //Import Class
     
    DecimalFormat precision = new DecimalFormat( "0.00" ) //create instance of object
    int myNum = 5.753432;
     
    precision.format(myNum); //call method

    More on DecimalFormat Class: DecimalFormat

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