How to REDUCE decimal values from a value of type 'double' in Java-CodePudding

This is probably a really simple question but, is there a simple way to go from

Double myLongNumber = 50.12345678998658576546

Double myLongNumber = 50.1234

I just want to reduce the number of decimal digits, not remove them all.

CodePudding user response：

If you really want to change that number, you can do something like

Double myNotSoLongNumber = Math.round(myLongNumber * 1E4) / 1E4;

If you want to display a Double with less fraction digits, use

String myLongNumberAsString = String.format("%.4f", myLongNumber);

CodePudding user response：

Please check below options

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.Locale;
import org.apache.commons.math3.util.Precision;

class DoubleTrimmer {
    public static void main(String[] args) {

        Double myLongNumber = 50.12345678998658576546;

        //Option1. just trim the number
        Double trimmedNumber  = Double.valueOf(String.format(Locale.ENGLISH, "%.4f", myLongNumber));
        System.out.println(trimmedNumber);

        //Option2. Round the number using BigDecimal
        trimmedNumber = round(myLongNumber, 4);
        System.out.println(trimmedNumber);

        //Option3. Round the number using Apache commons math
        trimmedNumber = Precision.round(myLongNumber, 4);
        System.out.println(trimmedNumber);
    }

    public static double round(double value, int places) {
        if (places < 0) throw new IllegalArgumentException();

        BigDecimal bd = BigDecimal.valueOf(value);
        bd = bd.setScale(places, RoundingMode.HALF_UP);
        return bd.doubleValue();
    }
}

CodePudding user response：

Use BigDecimal package

import java.math.BigDecimal;
public class ReduceDecimalNumbers {
    public static void main(String args[]){
        double myLongNumber = 50.12345678998658576546;
        int decimalsToConsider = 4;
        BigDecimal bigDecimal = new BigDecimal(myLongNumber );

        bigDecimal = new BigDecimal(myLongNumber );
        BigDecimal roundedValueWithDivideLogic = bigDecimal.divide(BigDecimal.ONE,decimalsToConsider,BigDecimal.ROUND_HALF_UP);
        System.out.println("Rounded value with Dividing by one = " roundedValueWithDivideLogic);

    }
}

output:

   Rounded value with Dividing by one = 50.1235

or you can try this

    public class round{
       public static void main(String args[]){
    
       double myLongNumber = 50.12345678998658576546;
       double roundOff = Math.round(myLongNumber *1E4)/1E4;
    
       System.out.println(String.format("%.4f", roundOff));   //%.4f defines decimal precision you want
      }
   }

output:

50.1235