How to calculate monetary values in Java

There are many monetary values calculation in the financial or e-commerce application, and there is one question that arises for this – Should we use double or float data type to represent the monetary values?

Answer: Always uses java.math.BigDecimal to represent the monetary values.

1. Double or Float?

Here is an example of using double and float to represent the monetary values in Java.

JavaMoney.java

package com.favtuts.classic;

import java.text.DecimalFormat;

public class JavaMoney {
    
    private static DecimalFormat df = new DecimalFormat("0.00");
    
    public static void main(String[] args) {
        representMonetaryValuesWithDoubleAndFloat();
    }

    static void representMonetaryValuesWithDoubleAndFloat() {

        System.out.println(2.00 - 1.1);
        System.out.println(2.00 - 1.2);
        System.out.println(2.00 - 1.3);
        System.out.println(2.00 - 1.4);
        System.out.println(2.00 - 1.5);
        System.out.println(2.00 - 1.6);
        System.out.println(2.00 - 1.7);
        System.out.println(2.00 - 1.8);
        System.out.println(2.00 - 1.9);
        System.out.println(2.00 - 2);

        System.out.println("--------------------");

        double i = 2.0;
        double j = 1.7;

        System.out.println("double : " + (i - j));
        System.out.println("double : " + df.format(i - j));

        float i2 = 2.0f;
        float j2 = 1.7f;

        System.out.println("float : " + (i2 - j2));
        System.out.println("float : " + df.format(i2 - j2));

    }
}

Output – It cannot calculate all the decimals precisely.

0.8999999999999999
0.8
0.7
0.6000000000000001
0.5
0.3999999999999999
0.30000000000000004
0.19999999999999996
0.10000000000000009
0.0
--------------------
double : 0.30000000000000004
double : 0.30
float : 0.29999995
float : 0.30

2. BigDecimal

To avoid the decimal issue above, we can use BigDecimal to represent the monetary values; furthermore, we can control the BigDecimal scale much more straightforward.

JavaMoney2.java

package com.favtuts.classic;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.text.DecimalFormat;

public class JavaMoney {

    private static DecimalFormat df = new DecimalFormat("0.00");

    public static void main(String[] args) {
        representMonetaryValuesWithBigDecimal();
    }

    static void representMonetaryValuesWithBigDecimal() {
        System.out.println("--- BigDecimal-----");
        System.out.println(BigDecimal.valueOf(2.00).subtract(BigDecimal.valueOf(1.1)));
        System.out.println(BigDecimal.valueOf(2.00).subtract(BigDecimal.valueOf(1.2)));
        System.out.println(BigDecimal.valueOf(2.00).subtract(BigDecimal.valueOf(1.3)));
        System.out.println(BigDecimal.valueOf(2.00).subtract(BigDecimal.valueOf(1.4)));
        System.out.println(BigDecimal.valueOf(2.00).subtract(BigDecimal.valueOf(1.5)));
        System.out.println(BigDecimal.valueOf(2.00).subtract(BigDecimal.valueOf(1.6)));
        System.out.println(BigDecimal.valueOf(2.00).subtract(BigDecimal.valueOf(1.7)));
        System.out.println(BigDecimal.valueOf(2.00).subtract(BigDecimal.valueOf(1.8)));
        System.out.println(BigDecimal.valueOf(2.00).subtract(BigDecimal.valueOf(1.9)));
        System.out.println(BigDecimal.valueOf(2.00).subtract(BigDecimal.valueOf(2)));

        System.out.println("--------------------");

        BigDecimal i = BigDecimal.valueOf(2.0);
        BigDecimal j = BigDecimal.valueOf(1.7);

        System.out.println("double : " + i.subtract(j));
        System.out.println("double : " + i.subtract(j).setScale(5, RoundingMode.HALF_UP));
    }
}

Output – BigDecimal performs exact decimal arithmetic.

--- BigDecimal-----
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
--------------------
double : 0.3
double : 0.30000

Download Source Code

$ git clone https://github.com/favtuts/java-core-tutorials-examples

$ cd java-basic/classic

References

• BigDecimal JavaDoc
• How to Use Java BigDecimal: A Tutorial
• Java 8 – How to Sum BigDecimal using Stream?