- A
Use a FileReader wrapped in a BufferedReader, and process each line in a loop.
Why wrong: Although it reads line by line, it requires manual handling of the resource closure to avoid leaks. The approach is correct but less concise than using Files.lines with try-with-resources.
- B
Use a FileInputStream to read bytes, then manually parse newline characters.
Why wrong: FileInputStream reads raw bytes, requiring low-level parsing, which is more error-prone and less efficient for line-oriented processing.
- C
Use Files.readAllLines to read the entire file into a List<String> and then iterate.
Why wrong: Files.readAllLines loads the entire file into memory, which would cause OutOfMemoryError for a large file.
- D
Use Files.lines with a try-with-resources block, and process each line using the stream.
Files.lines returns a Stream that reads lines lazily, and try-with-resources ensures the underlying file handle is closed automatically. This is the most efficient and idiomatic solution.
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. 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 developer needs to read a large text file (several gigabytes) line by line as efficiently as possible, processing each line without loading the entire file into memory. Which approach should the developer use?
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 Files.lines with a try-with-resources block, and process each line using the stream.
Option D is correct because `Files.lines` returns a `Stream<String>` that lazily reads lines from the file, processing them one at a time without loading the entire file into memory. The try-with-resources block ensures the underlying file handle is closed automatically, preventing resource leaks. This approach is specifically designed for efficient, memory-safe line-by-line processing of large files.
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 FileReader wrapped in a BufferedReader, and process each line in a loop.
Why it's wrong here
Although it reads line by line, it requires manual handling of the resource closure to avoid leaks. The approach is correct but less concise than using Files.lines with try-with-resources.
- ✗
Use a FileInputStream to read bytes, then manually parse newline characters.
Why it's wrong here
FileInputStream reads raw bytes, requiring low-level parsing, which is more error-prone and less efficient for line-oriented processing.
- ✗
Use Files.readAllLines to read the entire file into a List<String> and then iterate.
Why it's wrong here
Files.readAllLines loads the entire file into memory, which would cause OutOfMemoryError for a large file.
- ✓
Use Files.lines with a try-with-resources block, and process each line using the stream.
Why this is correct
Files.lines returns a Stream that reads lines lazily, and try-with-resources ensures the underlying file handle is closed automatically. This is the most efficient and idiomatic solution.
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 choose `BufferedReader` (Option A) because it is familiar, but they overlook that `Files.lines` is the modern, stream-based API that is both more idiomatic and safer for large files, and that `Files.readAllLines` (Option C) is a common pitfall for memory exhaustion.
Detailed technical explanation
How to think about this question
Under the hood, `Files.lines` uses a `BufferedReader` internally but wraps it in a `Stream` that supports lazy evaluation and parallel processing via `parallel()`. The stream is backed by a `ReadableByteChannel` that reads chunks of data, and lines are split using the `Pattern` `\R` (any Unicode linebreak), which handles various newline conventions (e.g., `\n`, `\r\n`, `\r`). In real-world scenarios, this is critical for log file analysis or ETL pipelines where files can exceed available RAM.
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.
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: Use Files.lines with a try-with-resources block, and process each line using the stream. — Option D is correct because `Files.lines` returns a `Stream<String>` that lazily reads lines from the file, processing them one at a time without loading the entire file into memory. The try-with-resources block ensures the underlying file handle is closed automatically, preventing resource leaks. This approach is specifically designed for efficient, memory-safe line-by-line processing of large files.
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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