How to Accurately Move Decimal Places in a Double Without Rounding Errors?

How to Move Decimal Places in a Double without Rounding Errors

To move a decimal place in a double, you might instinctively multiply by 0.1. However, this can introduce rounding errors, as 0.1 is not an exact representation in binary.

A More Accurate Way

Instead of using 0.1, it's preferable to use 100, which can be represented accurately in binary. To move a decimal place over, simply divide by 100:

double x = 1234;
x /= 100;

Why Rounding Is Unavoidable

Even with this approach, some rounding error is still present due to the limitations of floating-point representation. Double.toString() performs some rounding, but avoiding rounding altogether often requires using BigDecimal.

Comparison between x / 100 and x * 0.01

Note that x / 100 and x * 0.01 are not identical in terms of rounding error. The rounding error in the first expression depends on the value of x, while the 0.01 in the second has a fixed round error. This can lead to different results in certain cases.

Conclusion

Understanding the limitations of floating-point representation and using appropriate techniques can ensure accurate handling of decimal places in doubles, minimizing rounding errors that can arise from imprecise multiplication operations.

The above is the detailed content of How to Accurately Move Decimal Places in a Double Without Rounding Errors?. For more information, please follow other related articles on the PHP Chinese website!