Question 354 of 509

Arrays and Methods →easyMultiple ChoiceObjective-mapped

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."

1Z0-811 Arrays and Methods Practice Question

This 1Z0-811 practice question tests your understanding of arrays and methods. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

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?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

Question 1easymultiple choice

Full question →

A
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 wrong: 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.
B
public double average(double[] scores) { double sum = 0; for (double s : scores) sum += s; return sum / scores.length; }
Why wrong: Throws NullPointerException if scores is null, and divides by zero if empty.
C
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 wrong: Uses exceptions for control flow, which is inefficient and bad practice.
D
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; }
Explicitly avoids division by zero and handles null.

Full breakdown with real-world context →

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; }

Option D is correct because 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.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates may 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.

Detailed technical explanation

How to think about this question

In Java, primitive double arrays cannot contain null values; only reference types can be null. Division by zero with doubles does not throw an ArithmeticException but results in Infinity or NaN, so catching ArithmeticException is ineffective. The enhanced for loop over a null array throws a NullPointerException at runtime, not at compile time, making explicit null checks essential for robust code.

KKey Concepts to Remember

Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.

TExam Day Tips

Watch for words such as best, first, most likely and least administrative effort.
Review why wrong options are wrong, not only why the correct option is correct.

Key takeaway

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Real-world example

How this comes up in practice

A practitioner preparing for the 1Z0-811 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this 1Z0-811 question test?

Arrays and Methods — This question tests Arrays and Methods — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: 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; } — Option D is correct because 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.

What should I do if I get this 1Z0-811 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

Are there clue words in this question I should notice?

Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

About these practice questions

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Same concept, more angles

1 more ways 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: Option A is correct because 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.

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