Rounding a number off to certain number of places Java

Question

Good afternoon

Would just like to know what the easiest way would be of rounding a value of to a certain number of decimal places in Java.

With C#.

double answer;
double numberOne;
double numberTwo;
Console.WriteLine("Enter the numbers for your calculation");

numberOne = Double.Parse(Console.ReadLine());
numberTwo = Double.Parse(Console.ReadLine());
answer = numberOne / numberTwo;

Console.WriteLine(answer);
Console.WriteLine(Math.Round(answer, 3));

Kind regards

Look into using either a DecimalFormat object or String.format(...) — Hovercraft Full Of Eels, Nov 30 '11 at 14:52
possible duplicate of [How to round a number to n decimal places in Java](http://stackoverflow.com/questions/153724/how-to-round-a-number-to-n-decimal-places-in-java) — Bart Kiers, Nov 30 '11 at 14:53

score 4 · Answer 1 · edited May 23 '17 at 12:11

4

Well, I guess

(double)Math.round(answer * 1000) / 1000;

would do the trick. There might be other options though!

Edit: Just found this thread for a more detailed discussion:

How to round a number to n decimal places in Java

edited May 23 '17 at 12:11

Community

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answered Nov 30 '11 at 14:53

Willem Mulder

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@BartKiers Sorry about that. I can only see what I can see. – DJClayworth Nov 30 '11 at 15:07
@Willem, yeah, the Q&A you linked to contains much more info on rounding with Java (this question should really be closed as a duplicate). – Bart Kiers Nov 30 '11 at 15:08
+1: A slightly shorter answer `Math.round(answer*1000)/1000.0` – Peter Lawrey Nov 30 '11 at 15:24

score 3 · Accepted Answer · answered Nov 30 '11 at 14:52

3

double d = 3.12345;

DecimalFormat newFormat = new DecimalFormat("#.###");
double twoDecimal =  Double.valueOf(newFormat.format(d));

answered Nov 30 '11 at 14:52

Massimiliano Peluso

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score 3 · Answer 3 · answered Nov 30 '11 at 14:54

Look into using either a DecimalFormat object or String.format(...). For example

  double foo = 3.14159265;

  // note that printf uses the same formatter as Formatter 
  //as does String.format(...)
  System.out.printf("%.3f%n", foo);

  DecimalFormat dFormat = new DecimalFormat("0.###");
  System.out.println(dFormat.format(foo));

score 0 · Answer 4 · answered Nov 30 '11 at 15:27

0

A faster way to round (provided the number is not too large)

double d = (long)(x > 0 ? x * 1000 + 0.5 : x * 1000 - 0.5)/1e3;

Its about 3x faster than using Math.round (but will fail for numbers greater than 9 million trillion ;)

answered Nov 30 '11 at 15:27

Peter Lawrey

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Rounding a number off to certain number of places Java

4 Answers4