The answer is to use `Files.lines(path)` with try-with-resources, as this is the most efficient approach for reading a large file line by line in Java while minimizing memory footprint. This method returns a `Stream<String>` that lazily reads lines from the file, processing them one at a time without loading the entire file into memory, which is critical for files over 2 GB. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this question tests your understanding of the `java.nio.file.Files` API and stream-based I/O, often appearing as a trap where candidates mistakenly choose `BufferedReader.readLine()` in a loop or `Files.readAllLines()`, which loads the whole file into memory. Remember the mnemonic "Lazy Lines, Closed Streams" — the lazy loading of `Files.lines()` combined with try-with-resources ensures both memory efficiency and automatic resource cleanup.
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 company needs to read a large text file (over 2 GB) line by line in a Java application while minimizing memory footprint. Which approach is most efficient?
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(path) with try-with-resources
Option D is correct because `Files.lines(path)` returns a `Stream<String>` that lazily reads lines from the file, processing them one at a time without loading the entire file into memory. Combined with try-with-resources, the underlying `BufferedReader` is automatically closed, ensuring efficient resource management even for files over 2 GB.
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 Files.readAllLines(path)
Why it's wrong here
Reads entire file into memory, causing OOM for large files.
✗
Use FileOutputStream with read() loop
Why it's wrong here
Designed for binary output; not suitable for text line reading.
✗
Use Scanner with File and loop hasNextLine()
Why it's wrong here
Scanner is slower and less efficient than BufferedReader for line reading.
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 `Scanner` (Option C) because it is familiar from simple file reading, but they overlook its higher memory overhead and lack of automatic resource management compared to the stream-based `Files.lines()` with try-with-resources.
Trap categories for this question
Command / output trap
Designed for binary output; not suitable for text line reading.
Detailed technical explanation
How to think about this question
Under the hood, `Files.lines()` uses a `BufferedReader` with a default buffer size of 8 KB, reading chunks from the file and splitting lines on newline characters (`
`, `
`, or `
`). The stream is backed by a `Spliterator` that fetches lines on demand, allowing the JVM to garbage-collect each line after processing. In real-world scenarios like log analysis or ETL pipelines, this lazy approach prevents heap exhaustion and enables parallel processing via `parallelStream()` if needed.
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: Use Files.lines(path) with try-with-resources — Option D is correct because `Files.lines(path)` returns a `Stream<String>` that lazily reads lines from the file, processing them one at a time without loading the entire file into memory. Combined with try-with-resources, the underlying `BufferedReader` is automatically closed, ensuring efficient resource management even for files over 2 GB.
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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