The answer is to use `FileChannel.transferTo()` with explicit `position` and `count` parameters. This is correct because `transferTo()` leverages zero-copy I/O, allowing data to move directly between file system caches without passing through user-space buffers, which dramatically reduces context switches and memory overhead—essential for efficient large file copy operations exceeding 2 GB. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this question tests your understanding of NIO.2’s channel-based transfer methods versus traditional stream-based copying; a common trap is assuming `Files.copy()` is sufficient for huge files, but it lacks zero-copy optimization and can cause heap exhaustion. Remember that `transferTo()` handles large offsets via its `long position` parameter, avoiding integer overflow issues. Memory tip: think “zero-copy for zero overhead”—if the file is huge, transferTo is the true move.
1Z0-829 Java I/O API and Securing Applications Practice Question
This 1Z0-829 practice question tests your understanding of java i/o api and securing applications. Compare every option against the stated constraints before choosing — the best answer satisfies all requirements, not just the most obvious one. 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 a requirement to efficiently copy a large file (over 2 GB) from one path to another, which approach is most appropriate for Java NIO.2?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Using FileChannel.transferTo() with position and count
Option D is correct because `FileChannel.transferTo()` leverages zero-copy I/O, which allows data to be transferred directly between file system caches without unnecessary copying through user-space buffers. This is particularly efficient for large files (over 2 GB) as it minimizes context switches and memory overhead, and the method supports a `position` and `count` parameter to handle large file offsets correctly.
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.
Files.copy is efficient but may not be as performant as direct channel transfer for very large files.
✗
Using Files.readAllBytes() then Files.write()
Why it's wrong here
ReadAllBytes loads the entire file into memory, which is not feasible for a 2 GB file.
✗
Using FileInputStream and FileOutputStream with a buffer of 8192 bytes
Why it's wrong here
Traditional stream copying with a small buffer is inefficient for large files.
✓
Using FileChannel.transferTo() with position and count
Why this is correct
FileChannel.transferTo() leverages OS-level file transfer mechanisms, making it most efficient for large files.
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 often assume `Files.copy()` is the most straightforward and efficient NIO.2 method, but the exam specifically tests knowledge of zero-copy APIs (`FileChannel.transferTo()`) for large file operations, where the overhead of stream-based copying becomes a performance bottleneck.
Detailed technical explanation
How to think about this question
Under the hood, `FileChannel.transferTo()` delegates to the operating system's `sendfile()` system call on Linux or `TransmitFile()` on Windows, which moves data directly from one file descriptor to another within the kernel space, bypassing the application's heap entirely. This zero-copy approach not only reduces CPU usage but also avoids double buffering, making it ideal for high-throughput scenarios like copying large files or serving static content in web servers. A subtle behavior is that `transferTo()` may return fewer bytes than requested if the underlying channel is non-blocking or if the platform's maximum transfer size is exceeded, so the caller must loop until all bytes are transferred.
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.
Java I/O API and Securing Applications — This question tests Java I/O API and Securing Applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Using FileChannel.transferTo() with position and count — Option D is correct because `FileChannel.transferTo()` leverages zero-copy I/O, which allows data to be transferred directly between file system caches without unnecessary copying through user-space buffers. This is particularly efficient for large files (over 2 GB) as it minimizes context switches and memory overhead, and the method supports a `position` and `count` parameter to handle large file offsets correctly.
What should I do if I get this 1Z0-829 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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Question Discussion
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