How Can I Avoid Rounding Errors When Calculating with Doubles in Java?

Resolving Java Double Rounding Issues

In Java, performing calculations with double-precision floating-point numbers can sometimes lead to unexpected results due to rounding errors. To address this issue, it's essential to understand Java's floating-point arithmetic and adopt appropriate solutions.

When subtracting double values, small rounding errors may accumulate, resulting in incorrect calculations. Consider the following code snippet:

double tempCommission = targetPremium.doubleValue()*rate.doubleValue()/100d;
double netToCompany = targetPremium.doubleValue() - tempCommission;
double dCommission = request.getPremium().doubleValue() - netToCompany;

In this example, the expected commission result is 877.85, but the calculation yields 877.8499999999999 due to rounding errors.

Solution: Using BigDecimal

To ensure accurate calculations, it's recommended to use java.math.BigDecimal. This class provides precision floating-point arithmetic that addresses the limitations of double data types.

Rewriting the last line of code using BigDecimal:

BigDecimal commission = premium.subtract(netToCompany);

This approach eliminates rounding errors and produces the correct result:

System.out.println(commission + " = " + premium + " - " + netToCompany);

Output:

877.85 = 1586.6 - 708.75

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