Dynamically Convert Double to Int in Java and Kotlin Without Losing Precision

Описание: Discover how to efficiently parse a `Double` to `Int` in Java and Kotlin while preserving significant digits. Learn about the use of BigDecimal for this conversion.
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This video is based on the question https://stackoverflow.com/q/76814141/ asked by the user 'ibrahiem Mohamed' ( https://stackoverflow.com/u/3967916/ ) and on the answer https://stackoverflow.com/a/76814327/ provided by the user 'aled' ( https://stackoverflow.com/u/721855/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Dynamically Convert Double to Int in Java and Kotlin Without Losing Precision

Converting a Double to an Int in programming can often come with a significant challenge: precision loss. When you attempt to parse a decimal number (or double) to an integer, you run the risk of losing important digits or truncating the number incorrectly. This guide addresses the common problem of parsing Double values to Int in Java and Kotlin, specifically focusing on maintaining precision throughout the conversion process.

The Problem: Parsing Double to Int

Imagine you have a variety of Double values that you would like to convert into Int, and these values are guaranteed not to exceed the memory limit of an Int. You might think to simply convert using basic methods, but as shown in the examples below, simply removing the decimal point often yields inaccurate results:

DoubleDesired Int1.12311231.1111.12345112340.123451234You might know that one straightforward approach is to first convert the Double to a String, remove the decimal point, and then convert it to Int. However, this method is not the most effective or elegant solution. So, what's the better way?

The Solution: Using BigDecimal

To maintain precision and convert Double to Int effectively, utilizing BigDecimal is the key. BigDecimal allows for accurate representation of decimal numbers and prevents common pitfalls associated with float-point arithmetic.

Steps to Convert Double to Int Using BigDecimal

Here's a breakdown of how to perform the conversion using Java (the approach is similar in Kotlin).

Import BigDecimal: Start by importing the BigDecimal class which is available in java.math package.

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Create BigDecimal from Double: Use BigDecimal.valueOf(double) which accurately handles floating-point values without representation errors.

Get Unscaled Value: Call unscaledValue() on the BigDecimal instance. This will return the integer representation of the number without any scaling (decimal position).

Convert to Int: Then, convert the unscaled value to Int using intValueExact(), which will ensure that the value is precisely within the bounds of an Int.

Example Code

Here's a simple Java code snippet demonstrating the conversion:

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Output

The above code will output:

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Important Notes

The use of valueOf() is critical to avoid floating-point representation errors.

intValueExact() ensures that if the resulting value exceeds the Int range, an exception will be thrown, alerting you to potential overflow issues.

This method retains all significant digits from the original Double, making it a superior choice for scenarios involving decimal values.

Conclusion

When it comes to converting Double to Int in Java and Kotlin, using BigDecimal is a highly effective strategy that facilitates precision while avoiding common errors associated with direct conversions. By following the steps outlined in this post, you can ensure your data remains intact and accurate, even when it must be cast to integers.

This approach not only solves the immediate problem but also enhances your data handling capabilities when dealing with numeric values in programming.