Round to 2 decimal places

Question

Possible Duplicate:
Round a double to 2 significant figures after decimal point

I have:

mkm=((((amountdrug/fluidvol)*1000)/60)*infrate)/ptwt;

in my Java code. The code works fine but returns to several decimal places. How do I limit it to just 2 or 3?

Not the same. The linked dupe candidate discusses how to print a rounded number, not how to actually round the value stored in the variable. — sblom, Aug 29 '10 at 18:35

score 90 · Answer 1 · edited Nov 21 '13 at 09:32

90

Don't use doubles. You can lose some precision. Here's a general purpose function.

public static double round(double unrounded, int precision, int roundingMode)
{
    BigDecimal bd = new BigDecimal(unrounded);
    BigDecimal rounded = bd.setScale(precision, roundingMode);
    return rounded.doubleValue();
}

You can call it with

round(yourNumber, 3, BigDecimal.ROUND_HALF_UP);

"precision" being the number of decimal points you desire.

edited Nov 21 '13 at 09:32

IAmGroot

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answered Aug 29 '10 at 18:54

bluedevil2k

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Thanks bluedevil for taking the time to reply. I have tried your suggestion and get errors saying 'BigDecimal cannot be resolved to a type'. I'm afraid I'm new to this and need the idiots guide! – Alan Aug 29 '10 at 19:25
8

import java.math.BigDecimal – bluedevil2k Aug 29 '10 at 21:27

score 10 · Answer 2 · answered Oct 09 '11 at 04:48

10

Just use Math.round()

double mkm = ((((amountdrug/fluidvol)*1000f)/60f)*infrate)/ptwt;

mkm= (double)(Math.round(mkm*100))/100;

answered Oct 09 '11 at 04:48

Sasquatch

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3
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math.round won't work here as you arent getting 2 decimal places as per question – Adsy2010 Feb 28 '15 at 14:42

score 8 · Answer 3 · answered Feb 21 '12 at 17:12

8

double formattedNumber = Double.parseDouble(new DecimalFormat("#.##").format(unformattedNumber));

worked for me :)

answered Feb 21 '12 at 17:12

Paul

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score 1 · Answer 4 · answered Jun 18 '12 at 10:59

1

BigDecimal a = new BigDecimal("12345.0789"); a = a.divide(new BigDecimal("1"), 2, BigDecimal.ROUND_HALF_UP); //Also check other rounding modes System.out.println("a >> "+a.toPlainString()); //Returns 12345.08

answered Jun 18 '12 at 10:59

joy

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score 1 · Answer 5 · answered Aug 29 '10 at 18:40

1

Multiply by 1000, round, and divide back by 1000.

For basic Java: http://download.oracle.com/javase/tutorial/getStarted/index.html and http://download.oracle.com/javase/tutorial/java/index.html

answered Aug 29 '10 at 18:40

Thorbjørn Ravn Andersen

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Thanks Thorbjorn for the reply. In the distant past when I used to program in basic I would use the way you suggested (although it was int(x) not round). I cannot figure out how to do this in android java though. – Alan Aug 29 '10 at 19:29

score 0 · Answer 6 · answered Aug 29 '10 at 19:45

0

Try:

float number mkm = (((((amountdrug/fluidvol)*1000f)/60f)*infrate)/ptwt)*1000f;
int newNum = (int) mkm;
mkm = newNum/1000f; // Will return 3 decimal places

answered Aug 29 '10 at 19:45

travega

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Hi travega, I appriciate you taking the time to help me with this. I have copied and pasted the code you supplied, but am getting the error - 'syntax error, insert";" to complete LocalVariableDeclarationStatement'. I have checked the three ';' in the above code are in place. – Alan Aug 29 '10 at 20:25

score -2 · Answer 7 · answered Jul 18 '12 at 14:28

Create a class called Round and try using the method round as Round.round(targetValue, roundToDecimalPlaces) in your code

public class Round {

        public static float round(float targetValue, int roundToDecimalPlaces ){

            int valueInTwoDecimalPlaces = (int) (targetValue * Math.pow(10, roundToDecimalPlaces));

            return (float) (valueInTwoDecimalPlaces / Math.pow(10, roundToDecimalPlaces));
        }

    }

Round to 2 decimal places

7 Answers7

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