Round a double value to 10 digits in Java?

Question

I was looking for a simple way to round a double value to 10 digits but I didn't found even one way that look good to me, everything was too complicated. I hope someone could help me, for example: the value 0.83426945721236485 will become 0.8342694572

Thank you in advance.

Do you want to round it or just remove all digits after the 10th? Also, do you mean 10 digits or 10 decimal places? Cause right now, you have 11 digits. — RaminS, May 12 '16 at 21:33
@Gendarme That the number of digits after the point should be rounded to 10 digits (i.e – 0.1234567891) — Noah Levy, May 12 '16 at 21:37
@shmosel I saw this thread already but there was too complicated solutions — Noah Levy, May 12 '16 at 21:39
[This](http://stackoverflow.com/a/153753/5221346) looks incredibly simple to me. — RaminS, May 12 '16 at 21:41
@shmosel using only the Math class and some algebra, can you help me with that please? — Noah Levy, May 12 '16 at 21:41
@Gendarme But I do not get what the "d" means at the value "100000d" — Noah Levy, May 12 '16 at 21:42
[Here you go.](http://stackoverflow.com/questions/4331200/what-do-f-and-d-mean-at-the-end-of-numeric-literals) — RaminS, May 12 '16 at 21:44
@Gendarme And someone in the comments said that this method fails 90% of the cases — Noah Levy, May 12 '16 at 21:44
Well, you are looking for a simple solution to something that is not simple. Computers count in binary. [This](http://stackoverflow.com/a/154354/5221346) is probably as simple as it gets. — RaminS, May 12 '16 at 21:47
@Gendarme Thank you for that link, it made me learn something :) — Noah Levy, May 12 '16 at 21:48

score 3 · Answer 1 · answered May 12 '16 at 21:52

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Simple.

DecimalFormat df = new DecimalFormat("0.0000000000");
System.out.println(df.format(0.83426945721236485));

Take a look at the documentation: https://docs.oracle.com/javase/8/docs/api/java/text/DecimalFormat.html

answered May 12 '16 at 21:52

Sina Madani

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But I can't see how it rounds an already given value, looks like you just print a number on the screen. – Noah Levy May 12 '16 at 22:02
You're right. I spent the past 10 mins trying to come up with a primitive way to do rounding but couldn't find a short way without some nasty string concatenation and parsing. – Sina Madani May 12 '16 at 22:31

score 0 · Answer 2 · edited May 23 '17 at 11:46

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Decimal places are not meaningful internally for double, because it is a binary floating point.

You can, of course, choose to display it in any format supported by DecimalFormat, as suggested in a prior answer.

If you want a ten decimal place internal representation, you should be using BigDecimal with scale factor 10.

edited May 23 '17 at 11:46

Community

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answered May 13 '16 at 02:19

Patricia Shanahan

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Round a double value to 10 digits in Java?

2 Answers2