How to Convert String into BigDecimal in Java

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Introduction

Converting a String to a BigDecimal in Java is a common task when dealing with high-precision arithmetic, financial calculations, or when exact numeric representation is required. BigDecimal provides operations for arithmetic, scale manipulation, rounding, comparison, hashing, and format conversion. This blog post will explore different methods to convert a String to a BigDecimal in Java.

Table of Contents

1. Using BigDecimal(String) Constructor
2. Handling NumberFormatException
3. Setting Scale and Rounding Mode
4. Complete Example Program
5. Conclusion

1. Using BigDecimal(String) Constructor

The simplest way to convert a String to a BigDecimal is by using the BigDecimal constructor that takes a String as an argument. This constructor provides exact conversion without loss of precision.

Example:

import java.math.BigDecimal;

public class StringToBigDecimal {
    public static void main(String[] args) {
        String strValue = "12345.6789";

        // Convert string to BigDecimal using BigDecimal constructor
        BigDecimal bigDecimalValue = new BigDecimal(strValue);

        System.out.println("String value: " + strValue);
        System.out.println("BigDecimal value: " + bigDecimalValue);
    }
}

Output:

String value: 12345.6789
BigDecimal value: 12345.6789

Explanation:

• new BigDecimal(strValue) converts the string value to its BigDecimal representation.

2. Handling NumberFormatException

The BigDecimal constructor throws a NumberFormatException if the string does not represent a valid number. It is essential to handle this exception to ensure the robustness of your code.

Example:

import java.math.BigDecimal;

public class StringToBigDecimalWithExceptionHandling {
    public static void main(String[] args) {
        String strValue = "12345.6789a"; // Invalid numeric string

        try {
            // Attempt to convert string to BigDecimal
            BigDecimal bigDecimalValue = new BigDecimal(strValue);
            System.out.println("String value: " + strValue);
            System.out.println("BigDecimal value: " + bigDecimalValue);
        } catch (NumberFormatException e) {
            System.out.println("Invalid string format for BigDecimal: " + strValue);
        }
    }
}

Output:

Invalid string format for BigDecimal: 12345.6789a

Explanation:

• A try-catch block is used to handle the NumberFormatException that occurs when the string cannot be parsed as a BigDecimal.

3. Setting Scale and Rounding Mode

After converting a string to a BigDecimal, you might want to set a specific scale (number of decimal places) and rounding mode. The BigDecimal.setScale() method allows you to set the scale and rounding mode.

Example:

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

public class StringToBigDecimalWithScale {
    public static void main(String[] args) {
        String strValue = "12345.6789";

        // Convert string to BigDecimal
        BigDecimal bigDecimalValue = new BigDecimal(strValue);

        // Set scale and rounding mode
        BigDecimal scaledValue = bigDecimalValue.setScale(2, RoundingMode.HALF_UP);

        System.out.println("Original BigDecimal value: " + bigDecimalValue);
        System.out.println("Scaled BigDecimal value: " + scaledValue);
    }
}

Output:

Original BigDecimal value: 12345.6789
Scaled BigDecimal value: 12345.68

Explanation:

• bigDecimalValue.setScale(2, RoundingMode.HALF_UP) sets the scale to 2 decimal places and uses the HALF_UP rounding mode.

4. Complete Example Program

Here is a complete program that demonstrates all the methods discussed above to convert a String to a BigDecimal in Java.

Example Code:

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

public class StringToBigDecimalExample {
    public static void main(String[] args) {
        String strValue1 = "12345.6789";
        String strValue2 = "54321.1234";
        String strValue3 = "12345.6789a"; // Invalid numeric string

        // Using BigDecimal(String) Constructor
        BigDecimal bigDecimalValue1 = new BigDecimal(strValue1);
        System.out.println("Using BigDecimal(String) Constructor:");
        System.out.println("String value: " + strValue1);
        System.out.println("BigDecimal value: " + bigDecimalValue1 + "\n");

        // Handling NumberFormatException
        try {
            BigDecimal bigDecimalValue2 = new BigDecimal(strValue3);
            System.out.println("Handling NumberFormatException:");
            System.out.println("String value: " + strValue3);
            System.out.println("BigDecimal value: " + bigDecimalValue2 + "\n");
        } catch (NumberFormatException e) {
            System.out.println("Handling NumberFormatException:");
            System.out.println("Invalid string format for BigDecimal: " + strValue3 + "\n");
        }

        // Setting Scale and Rounding Mode
        BigDecimal bigDecimalValue3 = new BigDecimal(strValue2);
        BigDecimal scaledValue = bigDecimalValue3.setScale(2, RoundingMode.HALF_UP);
        System.out.println("Setting Scale and Rounding Mode:");
        System.out.println("Original BigDecimal value: " + bigDecimalValue3);
        System.out.println("Scaled BigDecimal value: " + scaledValue);
    }
}

Output:

Using BigDecimal(String) Constructor:
String value: 12345.6789
BigDecimal value: 12345.6789

Handling NumberFormatException:
Invalid string format for BigDecimal: 12345.6789a

Setting Scale and Rounding Mode:
Original BigDecimal value: 54321.1234
Scaled BigDecimal value: 54321.12

5. Conclusion

Converting a String to a BigDecimal in Java can be accomplished using the BigDecimal constructor. It is essential to handle the NumberFormatException to ensure your code is robust and can handle invalid input gracefully. Additionally, you can set the scale and rounding mode to achieve the desired precision. By understanding these different methods, you can choose the one that best fits your needs and coding style.

Happy coding!