1Z0-811 Primitives, Strings and Operators Practice Question
You are part of a team maintaining a legacy order processing system. The system stores order totals as primitive double values. A recent bug report shows that for very large orders (around $1,000,000.00), the total after adding a tax of 8.25% is sometimes off by a few cents. The calculation is: total = orderTotal * (1 + taxRate). The taxRate is defined as double taxRate = 0.0825; The orderTotal is received as a double. The application needs exact monetary precision to two decimal places. Which solution best addresses the precision issue while minimizing changes to the existing code?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use BigDecimal for all monetary calculations, replacing double everywhere.
BigDecimal provides exact arithmetic for monetary values. Replacing double with BigDecimal everywhere ensures precision. Math.round with scaling still uses double arithmetic before rounding, which may introduce errors. DecimalFormat only affects output, not internal calculation. Casting to float loses precision.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use BigDecimal for all monetary calculations, replacing double everywhere.
Why this is correct
Provides precise decimal arithmetic.
- ✗
Use DecimalFormat with RoundingMode.HALF_EVEN to format the output.
Why it's wrong here
Only formats output, calculation still imprecise.
- ✗
Use Math.round(total * 100) / 100.0 to round to two decimals.
Why it's wrong here
Double rounding may still have errors.
- ✗
Cast the result to float and then back to double to round.
Why it's wrong here
Loses precision.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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