How to do rounding

Question

I want to calculate the bill where need to do some rounding

What i expect is:

it should be nearest 10 cents. e.g:

10.17 -> 10.20 (round up)

10.11 -> 10.10 (round down)

I have tried to use:

grandTotal = Double.valueOf(String.format(Locale.ENGLISH, "%.2f", grandTotal));

but it will occur error when the total look like 12.15, 14.65, 19.85.

By right, it should round up, but my result shows it round down.

Never use `double` for monetary things. Use some integer type! — Gyro Gearless, May 11 '17 at 10:41
If you want rounding to just 1 decimal, you should use the format `%.1f` (not `%.2f`). Other than that, your code works nicely on my computer, also with 12.15 and 19.85 (they are rounded up to 12.2 and 19.9). What error are you seeing?? — Ole V.V., May 11 '17 at 11:10
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). — Ole V.V., May 11 '17 at 11:12

BladeCoder · Accepted Answer · 2017-05-11T11:06:16.840

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To represent monetary values with cents, you should only use integers (as cents), String or BigDecimal, not floats or doubles because floating-point values can't exactly represent all decimal values.

To round up to the first digit after comma, you can do:

BigDecimal value = new BigDecimal("10.17");
BigDecimal rounded = value.setScale(1, BigDecimal.ROUND_HALF_UP);

edited May 11 '17 at 11:06

answered May 11 '17 at 10:41

BladeCoder

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If I'm not mistaken, setScale rounds down by default, so the output of this snippet should be 10.1, isn't it? – Javi Armendáriz May 11 '17 at 10:45
Indeed, specifying the rounding mode is mandatory if the scale is reduced. I updated my answer. – BladeCoder May 11 '17 at 11:06

score 1 · Answer 2 · answered May 11 '17 at 10:53

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My two cents for a possible solution:

Double value = 14.65;
Double grandTotal = Math.round(value * 10)/10;

answered May 11 '17 at 10:53

Javi Armendáriz

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How to do rounding

2 Answers2