- A
Use FileInputStream with a buffered byte array and manually scan for newline characters.
Why wrong: This is low-level, error-prone, and does not solve the resource leak issue unless the stream is also properly closed. It introduces unnecessary complexity.
- B
Replace Files.lines with Files.newBufferedReader, wrapping it in a try-with-resources block.
Why wrong: This would also work but is not the best because Files.lines is more idiomatic for line-by-line streaming. However, the key issue is the missing closure; both approaches need try-with-resources. This option is plausible but not the best given that the original code used Files.lines.
- C
Use Files.readAllLines to load the entire file into memory and then iterate over the list.
Why wrong: This would cause OutOfMemoryError for a 5 GB file, making the problem worse.
- D
Wrap the Files.lines call in a try-with-resources block to ensure the stream is closed automatically.
By using try-with-resources, the stream's underlying file handle is closed when the block exits, fixing the resource leak. This is the minimal and correct fix.
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. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 developer is building a batch processing application that reads a large CSV file (approx. 5 GB) from a network file system, transforms each row, and writes the result to a database. The initial implementation uses Files.lines(path) to obtain a Stream<String>, processes each line with forEach, and then does not explicitly close the stream. After running for several minutes, the application slows down, and eventually throws an IOException: 'Too many open files'. The database writes are also failing intermittently. The developer needs to fix the application. The environment is Java 17 on Linux with default settings. Which course of action best resolves the issues?
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
Wrap the Files.lines call in a try-with-resources block to ensure the stream is closed automatically.
Option D is correct because `Files.lines(path)` returns a lazily populated `Stream<String>` that holds a file handle open. Without an explicit close, the underlying `FileChannel` and file descriptor are not released, leading to 'Too many open files' after processing many lines. Wrapping the stream in a try-with-resources block ensures `close()` is called automatically, releasing the file descriptor and preventing resource exhaustion.
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 FileInputStream with a buffered byte array and manually scan for newline characters.
Why it's wrong here
This is low-level, error-prone, and does not solve the resource leak issue unless the stream is also properly closed. It introduces unnecessary complexity.
- ✗
Replace Files.lines with Files.newBufferedReader, wrapping it in a try-with-resources block.
Why it's wrong here
This would also work but is not the best because Files.lines is more idiomatic for line-by-line streaming. However, the key issue is the missing closure; both approaches need try-with-resources. This option is plausible but not the best given that the original code used Files.lines.
- ✗
Use Files.readAllLines to load the entire file into memory and then iterate over the list.
Why it's wrong here
This would cause OutOfMemoryError for a 5 GB file, making the problem worse.
- ✓
Wrap the Files.lines call in a try-with-resources block to ensure the stream is closed automatically.
Why this is correct
By using try-with-resources, the stream's underlying file handle is closed when the block exits, fixing the resource leak. This is the minimal and correct fix.
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 overlook that `Files.lines` returns a stream that must be closed, confusing it with in-memory collections like `List` that do not hold system resources, or incorrectly assuming that `forEach` terminal operation automatically closes the stream.
Detailed technical explanation
How to think about this question
Under the hood, `Files.lines` opens a `FileChannel` and wraps it in a `Stream` backed by a `Spliterator` that reads lines lazily. The stream's `onClose` handler is registered to close the underlying channel, but if the stream is not closed (e.g., via try-with-resources or explicit `close()`), the file descriptor remains open until garbage collection, which may not happen promptly. On Linux, the default per-process file descriptor limit (ulimit -n) is often 1024, so processing a large file with many lines can exhaust this limit quickly, causing 'Too many open files' errors.
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 1Z0-829 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.
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What to study next
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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: Wrap the Files.lines call in a try-with-resources block to ensure the stream is closed automatically. — Option D is correct because `Files.lines(path)` returns a lazily populated `Stream<String>` that holds a file handle open. Without an explicit close, the underlying `FileChannel` and file descriptor are not released, leading to 'Too many open files' after processing many lines. Wrapping the stream in a try-with-resources block ensures `close()` is called automatically, releasing the file descriptor and preventing resource exhaustion.
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: Jul 4, 2026
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