Round to 2 decimal places

Question

Hi, I have the formular

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 to 2 or 3? Also can anyone recomend a book that teaches basic Android/java? Thanks

Edit 04/09/10 Thanks to everyone who took the time to try to help with this problem. Thanks to KennyTM who’s comment led me to the answer –

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

int precision = 100; //keep 2 digits

mkm = Math.floor(mkm * precision +.5)/precision;

Sorted! Thanks again to all.

Answer 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

Answer 2

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.

Answer 3

Try:

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