- A
Use a Stream to process the array without creating intermediate arrays.
Why wrong: Streams may create objects and are not necessarily zero-copy.
- B
Use a single temporary array and reuse it by copying data into it for each window.
Reuses one array, eliminating repeated allocations and reducing GC pressure.
- C
Use Arrays.copyOfRange() which is faster than System.arraycopy.
Why wrong: Still creates a new array each time.
- D
Use ArrayList instead of array to avoid copy.
Why wrong: ArrayList internally uses array, still requires copying and creates objects.
Question 255 of 509
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 team is developing a financial application that processes large arrays of market data. They have a method that calculates moving averages by copying a subarray for each window. The current implementation creates a new array for each window using System.arraycopy. The application is running slowly in production. The team identifies that the method is called millions of times per minute. The array is large and the window size is small. The garbage collector overhead is high due to many short-lived arrays. Which optimization should they apply to reduce object creation and improve performance?
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
✓
Use a single temporary array and reuse it by copying data into it for each window.
Option B is correct because reusing a single temporary array eliminates the repeated allocation of short-lived arrays for each window, directly reducing garbage collector overhead. The current implementation uses System.arraycopy to create a new array per window, which is the primary source of object churn. By allocating one array once and copying data into it for each window, the team minimizes object creation while still performing the necessary copy operation.
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.
- ✗
Use a Stream to process the array without creating intermediate arrays.
Why it's wrong here
Streams may create objects and are not necessarily zero-copy.
- ✓
Use a single temporary array and reuse it by copying data into it for each window.
Why this is correct
Reuses one array, eliminating repeated allocations and reducing GC pressure.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use Arrays.copyOfRange() which is faster than System.arraycopy.
Why it's wrong here
Still creates a new array each time.
- ✗
Use ArrayList instead of array to avoid copy.
Why it's wrong here
ArrayList internally uses array, still requires copying and creates objects.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The 1Z0-811 exam often tests the misconception that using a more modern API (like Streams or copyOfRange) automatically improves performance, when in fact the key optimization is reducing object allocation frequency.
Detailed technical explanation
How to think about this question
Under the hood, System.arraycopy is a native method that performs a fast memory copy, but each call to it with a new destination array triggers allocation on the heap. Reusing a pre-allocated array avoids this allocation, but care must be taken to ensure the array is large enough for the window size and that data from previous windows does not leak. In real-world high-frequency trading systems, such micro-optimizations are critical because garbage collection pauses can cause missed market events.
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: Use a single temporary array and reuse it by copying data into it for each window. — Option B is correct because reusing a single temporary array eliminates the repeated allocation of short-lived arrays for each window, directly reducing garbage collector overhead. The current implementation uses System.arraycopy to create a new array per window, which is the primary source of object churn. By allocating one array once and copying data into it for each window, the team minimizes object creation while still performing the necessary copy operation.
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.
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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.
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