Quick Answer
The correct choice is the snippet that first creates a destination array with `int[] copy = new int[arr.length];` and then calls `System.arraycopy(arr, 0, copy, 0, arr.length);`. This works because `System.arraycopy` is a native method that requires a pre-existing destination array to hold the copied elements—it does not allocate memory for you. On the Oracle Java Foundations 1Z0-811 exam, this question tests your understanding of array manipulation and the distinction between shallow copying with `arraycopy` versus using `clone()` or assignment. A common trap is forgetting to instantiate the destination array before calling the method, which would cause a `NullPointerException`. To remember the parameter order, think of the mnemonic "Source, Start, Destination, Start, Count"—the method copies from the source array starting at a given index into the destination array at its own starting index for a specified number of elements.
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.
Given an array arr of length 5, which code snippet correctly creates a copy using System.arraycopy?
System.arraycopy(arr, 0, copy, 0, arr.length);
Why wrong: copy is not declared or initialized.
int[] copy = Arrays.copyOf(arr, arr.length);
Why wrong: Uses Arrays.copyOf(), not arraycopy.
int[] copy = new int[arr.length]; System.arraycopy(arr, 0, copy, 0, arr.length);
Initializes copy then uses arraycopy correctly.
int[] copy = arr.clone();
Why wrong: Uses clone(), not arraycopy.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
int[] copy = new int[arr.length]; System.arraycopy(arr, 0, copy, 0, arr.length);
Option C is correct because it first declares and initializes a destination array `copy` of the same length as `arr`, then calls `System.arraycopy(arr, 0, copy, 0, arr.length)` to copy all 5 elements from `arr` into `copy`. This is the only option that uses `System.arraycopy` correctly, as the method requires a pre-existing destination array.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
System.arraycopy(arr, 0, copy, 0, arr.length);
Why it's wrong here
copy is not declared or initialized.
int[] copy = Arrays.copyOf(arr, arr.length);
Why it's wrong here
Uses Arrays.copyOf(), not arraycopy.
int[] copy = new int[arr.length]; System.arraycopy(arr, 0, copy, 0, arr.length);
Why this is correct
Initializes copy then uses arraycopy correctly.
Related concept
Read the scenario before looking for a memorised answer.
int[] copy = arr.clone();
Why it's wrong here
Uses clone(), not arraycopy.
Common exam traps
Oracle often tests the requirement to use a specific method name exactly as stated in the question, so candidates mistakenly choose options that achieve the same result (like `Arrays.copyOf` or `clone()`) but do not use the mandated `System.arraycopy` call.
Detailed technical explanation
`System.arraycopy` is a native method that performs a shallow copy of array elements, and it is more efficient than a manual loop for large arrays because it uses a low-level memory copy operation. The method signature is `public static void arraycopy(Object src, int srcPos, Object dest, int destPos, int length)`, and it throws `NullPointerException` if either array is null, `ArrayStoreException` if a type mismatch occurs, and `IndexOutOfBoundsException` if the copy would exceed array bounds. In real-world scenarios, this is often used in buffer management or when implementing custom collection classes where performance is critical.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Arrays and Methods — This question tests Arrays and Methods — Read the scenario before looking for a memorised answer..
The correct answer is: int[] copy = new int[arr.length]; System.arraycopy(arr, 0, copy, 0, arr.length); — Option C is correct because it first declares and initializes a destination array `copy` of the same length as `arr`, then calls `System.arraycopy(arr, 0, copy, 0, arr.length)` to copy all 5 elements from `arr` into `copy`. This is the only option that uses `System.arraycopy` correctly, as the method requires a pre-existing destination array.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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