Question 281 of 481
1Z0-811 Arrays and Methods Practice Question
A method 'public static double average(int[] numbers) { int sum = 0; for (int i = 0; i < numbers.length; i++) sum += numbers[i]; return sum / numbers.length; }' is called with array {10, 20, 30}. What change is needed to return the correct average?
⚠ Common exam trap
Oracle often tests the distinction between integer and floating-point division in Java, trapping candidates who overlook that dividing two ints always truncates the decimal, even when assigned to a double variable or returned from a double method.
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
✓
Change 'sum / numbers.length' to '(double) sum / numbers.length'
The method performs integer division because both `sum` (int) and `numbers.length` (int) are integers, truncating the fractional part. Casting `sum` to `double` before division forces floating-point arithmetic, preserving the decimal value. For the array {10, 20, 30}, the correct average is 20.0, but integer division yields 20 (truncated from 20.0, though here it matches by coincidence; for non-integer averages like {10, 20, 31}, the error would be obvious).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Change the loop to for (int i = 1; i <= numbers.length; i++)
Why it's wrong here
Loop index is off-by-one and does not solve division issue.
- ✓
Change 'sum / numbers.length' to '(double) sum / numbers.length'
Why this is correct
The original code performs integer division because both `sum` and `numbers.length` are integer types. This truncates any fractional part, leading to an incorrect average for inputs that do not divide evenly. Casting `sum` to `double` before the division forces floating-point arithmetic. This ensures `numbers.length` is also promoted to `double`, allowing the calculation to produce a precise decimal result, satisfying the requirement to return the correct average.
- ✗
Change return type to int
Why it's wrong here
Still integer division, and average may be fractional.
- ✗
Add a second parameter for the length
Why it's wrong here
Unnecessary and changes signature.
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Last reviewed: Jun 30, 2026
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