The correct answer is that the method modifies the original array. This is because Java uses pass-by-value for method arguments, but when the argument is an object reference—like an array—the value being passed is the memory address of that array. Inside the method, any changes to the array elements directly affect the same underlying object in the caller’s scope, making this an in-place modification. On the Oracle Java Foundations 1Z0-811 exam, this concept often appears in questions about array manipulation, testing whether you understand that reassigning the reference itself (e.g., arr = new int[5]) would not affect the caller, but mutating elements like swapping values does. A common trap is confusing pass-by-value of the reference with pass-by-reference; remember that you can change the object’s contents, but not which object the caller’s variable points to. Memory tip: think of the reference as a house address—you can redecorate the house (modify elements), but you cannot move the house to a new street (reassign the caller’s reference).
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 method is designed to reverse an array of integers. The method signature is: public static void reverse(int[] arr). The method correctly reverses the array. Which statement is true about the method?
Since it returns void, the only way to provide the reversed array to the caller is by modifying the input array.
B
It returns a new array that is the reverse of the input.
Why wrong: The method has a void return type, so it cannot return a new array.
C
It cannot be called with a null array.
Why wrong: While it's true that calling with null would cause a NullPointerException, this is not the most relevant statement about the method's behavior.
D
It uses pass-by-value, so the original array is unchanged.
Why wrong: Pass-by-value applies to the reference; the array object itself is shared, so modifications are visible to the caller.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It modifies the original array.
Option A is correct because the method receives a reference to the array (pass-by-value of the reference), so any modifications made to the array elements inside the method directly affect the original array object in the caller's scope. Since the method reverses the array in-place by swapping elements, the original array is mutated.
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.
✓
It modifies the original array.
Why this is correct
Since it returns void, the only way to provide the reversed array to the caller is by modifying the input array.
Related concept
Read the scenario before looking for a memorised answer.
✗
It returns a new array that is the reverse of the input.
Why it's wrong here
The method has a void return type, so it cannot return a new array.
✗
It cannot be called with a null array.
Why it's wrong here
While it's true that calling with null would cause a NullPointerException, this is not the most relevant statement about the method's behavior.
✗
It uses pass-by-value, so the original array is unchanged.
Why it's wrong here
Pass-by-value applies to the reference; the array object itself is shared, so modifications are visible to the caller.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Oracle often tests the misconception that Java uses pass-by-reference for objects; the trap here is that candidates think 'pass-by-value' means the original array cannot be changed, but in reality, the reference is passed by value, allowing mutation of the array's contents.
Detailed technical explanation
How to think about this question
In Java, arrays are objects, and when passed to a method, the reference to the array is passed by value. This means the method can modify the contents of the array (e.g., arr[i] = arr[j]) because it operates on the same underlying object. However, reassigning the reference itself (e.g., arr = new int[5]) inside the method would not affect the caller's reference. This distinction is critical for understanding mutability and aliasing in Java.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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.
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: It modifies the original array. — Option A is correct because the method receives a reference to the array (pass-by-value of the reference), so any modifications made to the array elements inside the method directly affect the original array object in the caller's scope. Since the method reverses the array in-place by swapping elements, the original array is mutated.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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 →
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. Consider a method that takes an int array and modifies it: public static void doubleArray(int[] arr) { for (int i = 0; i < arr.length; i++) { arr[i] *= 2; } }. What is the output of: int[] nums = {1, 2, 3}; doubleArray(nums); System.out.println(nums[1]);
medium
✓ A.4
B.8
C.2
D.3
Why A: Option A is correct because the method `doubleArray` multiplies each element of the array by 2. The array `nums` is passed by reference, so modifications inside the method affect the original array. After execution, `nums[1]` (originally 2) becomes 4, which is printed.
Variation 2. Which TWO methods correctly modify the passed array in place?
medium
✓ A.public void zeroOut(int[] a) { for (int i = 0; i < a.length; i++) a[i] = 0; }
✓ B.public void incrementEach(int[] a) { for (int i = 0; i < a.length; i++) a[i]++; }
C.public void reset(int[] a) { a = new int[10]; }
D.public void swap(int[] a) { int[] temp = a; a = new int[1]; a[0] = temp[0]; }
E.public void setFirst(int[][] a) { a = new int[1][1]; a[0][0] = 5; }
Why A: Option A is correct because it directly modifies each element of the passed array by assigning 0 to a[i] within the loop. In Java, when an array is passed to a method, the method receives a reference to the same array object, so changes to the array's elements are reflected in the caller's array.
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Question Discussion
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