Why Does Double Subtraction in Java Lead to Inaccurate Results, and How Can BigDecimal Solve This?

How to Resolve a Java Rounding Double Issue

When working with doubles, precision inaccuracies can arise, leading to unexpected calculation results. One such issue is the rounding that occurs during double subtraction, as exemplified in the provided code snippet.

In this example, the subtraction of tempCommission from targetPremium results in a value of 708.75, while the expected value is 708.76. This difference is due to the use of double-precision floating-point numbers, which have inherent limitations in their accuracy.

To resolve this issue and ensure correct calculations, consider using the java.math.BigDecimal class, which provides precise decimal arithmetic. BigDecimal offers greater control over the precision of floating-point operations, eliminating the rounding errors associated with double subtraction.

In the revised code snippet, BigDecimal is used to perform the subtraction of netToCompany from premium, resulting in the expected value of 877.85. This demonstrates the effectiveness of BigDecimal in handling precise decimal calculations, eliminating the rounding issues encountered with doubles:

import java.math.BigDecimal;

BigDecimal premium = BigDecimal.valueOf("1586.6");
BigDecimal netToCompany = BigDecimal.valueOf("708.75");
BigDecimal commission = premium.subtract(netToCompany);
System.out.println(commission + " = " + premium + " - " + netToCompany);

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