- A
A Selector can be used to manage multiple non-blocking channels.
A Selector can monitor multiple non-blocking channels.
- B
Files.walk() returns a Stream<Path> that lazily populates.
Files.walk() returns a Stream<Path> that traverses the directory tree.
- C
FileChannel operations are always non-blocking.
Why wrong: FileChannel is blocking by default; can be set to non-blocking but not always.
- D
BufferedInputStream extends FilterInputStream.
Why wrong: True, but it's about java.io, not NIO.2.
- E
Paths.get() is a factory method for obtaining a Path object.
Paths.get() is a convenient way to create Path instances.
Quick Answer
The correct answer is that Paths.get() is a factory method for obtaining a Path object, but the deeper truth tested here is how Java NIO.2’s Selector fundamentally interacts with blocking I/O. A Selector is designed to manage multiple non-blocking channels, allowing a single thread to monitor I/O readiness across many channels, which is the core of NIO.2’s multiplexed I/O model; channels must be configured in non-blocking mode to be registered with a Selector. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this question tests your understanding of the distinction between the blocking I/O of traditional streams and the non-blocking, event-driven model of NIO.2’s Selector, Files.walk(), and Paths.get(). A common trap is assuming a Selector works with blocking channels, but it strictly requires non-blocking mode. Memory tip: “Selector selects non-blocking channels only—blocking channels are left out.”
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. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Which THREE statements are true about Java NIO.2 and its interaction with blocking I/O? (Choose three.)
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
A Selector can be used to manage multiple non-blocking channels.
Option A is correct because a Selector in Java NIO.2 is specifically designed to manage multiple non-blocking channels, enabling a single thread to monitor I/O readiness across many channels. This is a core feature of the NIO.2 multiplexed I/O model, where channels must be configured in non-blocking mode to be registered with a Selector.
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.
- ✓
A Selector can be used to manage multiple non-blocking channels.
Why this is correct
A Selector can monitor multiple non-blocking channels.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Files.walk() returns a Stream<Path> that lazily populates.
Why this is correct
Files.walk() returns a Stream<Path> that traverses the directory tree.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
FileChannel operations are always non-blocking.
Why it's wrong here
FileChannel is blocking by default; can be set to non-blocking but not always.
- ✗
BufferedInputStream extends FilterInputStream.
Why it's wrong here
True, but it's about java.io, not NIO.2.
- ✓
Paths.get() is a factory method for obtaining a Path object.
Why this is correct
Paths.get() is a convenient way to create Path instances.
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 confuse the blocking nature of FileChannel with NIO.2's non-blocking channels, or they mistakenly think BufferedInputStream is a correct answer because it is a valid I/O class, but it is not related to NIO.2 and does not fit the question's focus on NIO.2 and blocking I/O interaction.
Detailed technical explanation
How to think about this question
Under the hood, a Selector uses an operating system-specific multiplexing mechanism (e.g., epoll on Linux, kqueue on macOS, or IOCP on Windows) to efficiently poll registered channels for events like connect, accept, read, or write. The Files.walk() method returns a lazily-populated Stream<Path> that traverses the file tree depth-first, using a DirectoryStream internally to avoid loading the entire tree into memory, which is critical for large directory structures.
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.
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FAQ
Questions learners often ask
What does this 1Z0-829 question test?
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: A Selector can be used to manage multiple non-blocking channels. — Option A is correct because a Selector in Java NIO.2 is specifically designed to manage multiple non-blocking channels, enabling a single thread to monitor I/O readiness across many channels. This is a core feature of the NIO.2 multiplexed I/O model, where channels must be configured in non-blocking mode to be registered with a Selector.
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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Last reviewed: Jun 25, 2026
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