CODEWITHSUNDEEP
java
upv
upv

Reputation: 539

android number format

In my app want to round a double to 2 significant figures after decimal point. I tried the code below.

public static double round(double value, int places) {
long factor = (long) Math.pow(10, places);
value = value * factor;
long tmp = Math.round(value);
return (double) tmp / factor;
}

also i tried

double val = ....;
val = val*100;
val = (double)((int) val);
val = val /100;

both code do not working for me.

Thanks in advance....

Upvotes: 7

Views: 19777

Answers (6)

Boris Karloff
Boris Karloff

Reputation: 1328

I took the decision to use all as int. In this way no problem.

DecimalFormatSymbols currencySymbol = DecimalFormatSymbols.getInstance();
NumberFormat numberF = NumberFormat.getInstance();

after...

numberF.setMaximumFractionDigits(2);
numberF.setMinimumFractionDigits(2);

TextView tv_total = findViewById(R.id.total);
int total = doYourStuff();//calculate the prices
tv_total.setText(numberF.format(((double)total)/100) + currencySymbol.getCurrencySymbol());

Upvotes: 0

ratchet freak
ratchet freak

Reputation: 48186

Or you can use a java.text.DecimalFormat:

String string = new DecimalFormat("####0.00").format(val);

Upvotes: 6

Ian McLaird
Ian McLaird

Reputation: 5585

As Grammin said, if you're trying to represent money, use BigDecimal. That class has support for all sorts of rounding, and you can set you desired precision exactly.

But to directly answer your question, you can't set the precision on a double, because it's floating point. It doesn't have a precision. If you just need to do this to format output, I'd recommend using a NumberFormat. Something like this:

NumberFormat nf = NumberFormat.getInstance();
nf.setMinimumFractionDigits(2);
nf.setMaximumFractionDigits(2);
String output = nf.format(val);

Upvotes: 20

Jim Blackler
Jim Blackler

Reputation: 23169

Your code appears to work to me

double rounded = round(0.123456789, 3);
System.out.println(rounded);

>0.123

Edit: just seen your new comment on your question. This is a formatting problem, not a maths problem.

Upvotes: 0

Riccardo Cossu
Riccardo Cossu

Reputation: 2739

As Gramming suggested you could use BigDecimals for that, or NumberFormat tobe sure about the number of shown figures

Upvotes: 0

Grammin
Grammin

Reputation: 12205

I would recommend using BigDecimal if you are trying to represent currency.

This example may be helpful.

Upvotes: 3

Related Questions