Question 354 of 481
Average Method with Null and Empty Arrays in Java
A developer is writing a method to compute the average of an array of scores. The method should handle edge cases gracefully. The scores array may be empty or contain null values if the collection was interrupted. The scores are stored as primitive doubles. Which implementation is safest and follows best practices?
Quick Answer
The correct answer is the implementation that checks for both null and empty arrays before computing the average, returning 0.0 in either edge case. This is safest because a null array would throw a NullPointerException if accessed without a guard, and an empty array would cause a division by zero when calculating sum divided by length. The solution uses an explicit null check followed by a ternary operator to handle the empty array, ensuring the method gracefully returns 0.0 instead of crashing. On the Oracle Java Foundations 1Z0-811 exam, this tests your understanding of defensive programming and edge case handling with primitive arrays—a common trap is forgetting the null check or using exception handling like try-catch for flow control, which is not best practice. Remember the memory tip: "Check null first, then check length—zero length means zero average."
⚠ Common exam trap
It's easy for candidates to think catching NullPointerException or using a single check for null is sufficient, but they overlook that an empty array requires a separate check to avoid division by zero, and that double division by zero does not throw an exception.
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
✓
public double average(double[] scores) { if (scores == null) return 0.0; double sum = 0; for (double s : scores) sum += s; return scores.length == 0 ? 0.0 : sum / scores.length; }
It explicitly checks for both a null array and an empty array before performing the division. The null check prevents a NullPointerException, and the ternary operator `scores.length == 0 ? 0.0 : sum / scores.length` avoids division by zero when the array is empty. This follows best practices by handling edge cases without relying on exceptions for flow control.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
public double average(double[] scores) { if (scores == null || scores.length == 0) return 0.0; double sum = 0; for (double s : scores) sum += s; return sum / scores.length; }
Why it's wrong here
Handles null and empty, but returns 0.0 which may be misleading; it's safe but not the best practice as it doesn't differentiate.
- ✗
public double average(double[] scores) { double sum = 0; for (double s : scores) sum += s; return sum / scores.length; }
Why it's wrong here
Throws NullPointerException if scores is null, and divides by zero if empty.
- ✗
public double average(double[] scores) { try { double sum = 0; for (double s : scores) sum += s; return sum / scores.length; } catch (NullPointerException | ArithmeticException e) { return 0.0; } }
Why it's wrong here
Uses exceptions for control flow, which is inefficient and bad practice.
- ✓
public double average(double[] scores) { if (scores == null) return 0.0; double sum = 0; for (double s : scores) sum += s; return scores.length == 0 ? 0.0 : sum / scores.length; }
Why this is correct
Explicitly avoids division by zero and handles null.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more way this is tested on 1Z0-811
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A method is designed to compute the average of an array of test scores. What should the method return if the array is empty (length 0)?
easy- ✓ A.Return 0.0
- B.Do not compile; requires a return of type double
- C.Throw a RuntimeException
- D.Return null
Why A: The method should return 0.0 for an empty array to avoid division by zero and to provide a safe default value. In Java, an empty array has length 0, and computing the average would require dividing by zero, which throws an ArithmeticException. Returning 0.0 is a common convention for empty collections, as it allows the caller to handle the result gracefully without crashing.
Last reviewed: Jun 25, 2026
This 1Z0-811 practice question is part of Courseiva's free Oracle certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 1Z0-811 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.