Java Programming Help: How to set Precision for double value

You can set Precision for double value either via BigDecimal or DecimalFormat, depending on what you want to do with the value later.

1. Setting double precision using DecimalFormat

DecimalFormatExample.java


package com.codersarts;

import java.text.DecimalFormat;

public class DecimalFormatExample {

   // setting precision upto 2 decimal point
    private static DecimalFormat df = new DecimalFormat("#.##");

    public static void main(String[] args) {

        double piValue = 3.14159265359;
        System.out.println("double : " + piValue);
        System.out.println("double : " + df.format(piValue));    //3.14

    }

}

Output

double : 3.14159265359
double : 3.14

2. Setting double precision using BigDecimal

//BigDecimalFormatExample.java

package com.codersarts;

import java.math.RoundingMode;
import java.math.BigDecimal;

public class BigDecimalFormatExample {

    public static void main(String[] args) {

        double piValue = 3.14159265359;
        System.out.println("double : " + piValue);

        BigDecimal bd = new BigDecimal(piValue).setScale(2, RoundingMode.HALF_UP);
        double newInput = bd.doubleValue();

        System.out.println("double : " + newInput);

    }

}

3. Setting double precision using String.format


package com.codersarts;

public class StringFormatExample {

    public static void main(String[] args) {

        double input = 3.14159265359;
        System.out.println("double : " + input);
        System.out.println("double : " + String.format("%.2f", input));
        System.out.format("double : %.2f", input);

    }

}

Note: You can't set the precision of a double (or Double) to a specified number of decimal digits, because floating-point values don't have decimal digits. They have binary digits.

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