How do I limit the number of decimals printed for a double?

Question

This program works, except when the number of nJars is a multiple of 7, I will get an answer like $14.999999999999998. For 6, the output is 14.08. How do I fix exceptions for multiples of 7 so it will display something like $14.99?

import java.util.Scanner;
public class Homework_17
{
 private static int nJars, nCartons, totalOunces, OuncesTolbs, lbs;

 public static void main(String[] args)
  {
   computeShippingCost();
  }

  public static void computeShippingCost()
  {
   System.out.print("Enter a number of jars: ");
   Scanner kboard = new Scanner (System.in);
   nJars = kboard.nextInt();
   int nCartons = (nJars + 11) / 12;
   int totalOunces = (nJars * 21) + (nCartons * 25);
   int lbs = totalOunces / 16;
   double shippingCost =  ((nCartons * 1.44) + (lbs + 1) * 0.96) + 3.0;

   System.out.print("$" + shippingCost);
   }
}

As it seems like it is homework I'll give just a hint: *Use DecimalFormat class.* — Harry Joy, Jan 17 '12 at 13:24
What's the problem in using class provided by Java? It is not any third party class. — Harry Joy, Jan 17 '12 at 13:28
duplicate of http://stackoverflow.com/questions/8819842/best-way-to-format-a-double-value-to-2-decimal-places — Rajesh Pantula, Jan 17 '12 at 13:29
IRL you shouldn't use floating point numbers for monetary calculations. Use BigDecimal/long/int instead. See http://stackoverflow.com/questions/3730019/why-not-use-double-or-float-to-represent-currency — COME FROM, Jan 17 '12 at 13:55

score 56 · Accepted Answer · edited Jan 17 '12 at 15:55

56

Use a DecimalFormatter:

double number = 0.9999999999999;
DecimalFormat numberFormat = new DecimalFormat("#.00");
System.out.println(numberFormat.format(number));

Will give you "0.99". You can add or subtract 0 on the right side to get more or less decimals.

Or use '#' on the right to make the additional digits optional, as in with #.## (0.30) would drop the trailing 0 to become (0.3).

edited Jan 17 '12 at 15:55

Louis Wasserman

182,351
25
326
397

answered Jan 17 '12 at 13:26

Alex

2,355
4
22
35

4

IMHO, Don't use `Double` when you mean to use `double`. – Peter Lawrey Jan 17 '12 at 13:32

KV Prajapati · Answer 2 · 2012-01-17T13:38:11.770

11

If you want to print/write double value at console then use System.out.printf() or System.out.format() methods.

System.out.printf("\n$%10.2f",shippingCost);
System.out.printf("%n$%.2f",shippingCost);

edited Jan 17 '12 at 13:38

answered Jan 17 '12 at 13:29

KV Prajapati

92,042
19
143
183

1

`"$%.2f"` will be ok as it does not print any preceding space as in `"$%10.2f"`. Anyways +1. – Harry Joy Jan 17 '12 at 13:32

score 5 · Answer 3 · answered Jan 17 '12 at 13:27

Check out DecimalFormat: http://docs.oracle.com/javase/6/docs/api/java/text/DecimalFormat.html

You'll do something like:

new DecimalFormat("$#.00").format(shippingCost);

Or since you're working with currency, you could see how NumberFormat.getCurrencyInstance() works for you.

score 1 · Answer 4 · answered Sep 10 '16 at 19:09

Formatter class is also a good option. fmt.format("%.2f", variable); 2 here is showing how many decimals you want. You can change it to 4 for example. Don't forget to close the formatter.

 private static int nJars, nCartons, totalOunces, OuncesTolbs, lbs;

 public static void main(String[] args)
  {
   computeShippingCost();
  }

  public static void computeShippingCost()
  {
   System.out.print("Enter a number of jars: ");
   Scanner kboard = new Scanner (System.in);
   nJars = kboard.nextInt();
   int nCartons = (nJars + 11) / 12;
   int totalOunces = (nJars * 21) + (nCartons * 25);
   int lbs = totalOunces / 16;


   double shippingCost =  ((nCartons * 1.44) + (lbs + 1) * 0.96) + 3.0;

     Formatter fmt = new Formatter();
     fmt.format("%.2f", shippingCost);

   System.out.print("$" + fmt);

   fmt.close();

}

score 0 · Answer 5 · answered Nov 09 '16 at 19:27

okay one other solution that I thought of just for the fun of it would be to turn your decimal into a string and then cut the string into 2 strings, one containing the point and the decimals and the other containing the Int to the left of the point. after that you limit the String of the point and decimals to 3 chars, one for the decimal point and the others for the decimals. then just recombine.

double shippingCost = ((nCartons * 1.44) + (lbs + 1) * 0.96) + 3.0;
String ShippingCost = (String) shippingCost;
String decimalCost = ShippingCost.subString(indexOf('.'),ShippingCost.Length());
ShippingCost = ShippingCost.subString(0,indexOf('.'));
ShippingCost = ShippingCost + decimalCost;

There! Simple, right?

score 0 · Answer 6 · answered Jan 17 '12 at 13:25

0

Use the DecimalFormat class to format the double

answered Jan 17 '12 at 13:25

Jrom

851
1
8
19

score 0 · Answer 7 · answered Jan 17 '12 at 13:26

0

You use the String.format() method.

answered Jan 17 '12 at 13:26

Wernsey

5,362
21
38

How do I limit the number of decimals printed for a double?

7 Answers7

Linked