How To Calculate Exact Values In Java Using Double Vs BigDecimal

How To Calculate Exact Values In Java Using Double Vs BigDecimal

Here is an example to use double to represent the values in Java.

public class ProblemWithDouble {

public static void main(String[] args)

{

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

                  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);

}

}

output:

--- Normal Print-----

0.8999999999999999

0.8

0.7

0.6000000000000001

0.5

0.3999999999999999

0.30000000000000004

0.19999999999999996

0.10000000000000009

0.0

In the output, it cannot calculate all double decimals precisely.

Solution: using BigDecimal

import java.math.BigDecimal;

public class ProblemWithDouble {

public static void main(String[] args)

{

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

           System.out.println(new BigDecimal("2.00").subtract(new BigDecimal("1.1")));

           System.out.println(new BigDecimal("2.00").subtract(new BigDecimal("1.2")));

           System.out.println(new BigDecimal("2.00").subtract(new BigDecimal("1.3")));

           System.out.println(new BigDecimal("2.00").subtract(new BigDecimal("1.4")));

           System.out.println(new BigDecimal("2.00").subtract(new BigDecimal("1.5")));

           System.out.println(new BigDecimal("2.00").subtract(new BigDecimal("1.6")));

           System.out.println(new BigDecimal("2.00").subtract(new BigDecimal("1.7")));

           System.out.println(new BigDecimal("2.00").subtract(new BigDecimal("1.8")));

           System.out.println(new BigDecimal("2.00").subtract(new BigDecimal("1.9")));

           System.out.println(new BigDecimal("2.00").subtract(new BigDecimal("2")));

}

}

output:

--- BigDecimal-----

0.90

0.80

0.70

0.60

0.50

0.40

0.30

0.20

0.10

0.00

BigDecimal performs exact decimal arithmetic.

Conclusion

In Java, it’s recommended to use BigDecimal to represent the monetary calculations. However BigDecimal calculations are slower than those with primitive data type calculations, which may be an issue for heavy decimal calculations program, but there’s should be no problem for most programs.