The correct choice is to use FileChannel with a ByteBuffer to read in chunks. This approach leverages the operating system’s native I/O, allowing you to read a very large file efficiently by processing data in configurable byte buffers, which minimizes memory overhead and avoids loading the entire file into heap space. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this question tests your understanding of NIO.2 and the trade-offs between stream-based readers, which suffer from high context switching and internal buffering, and channel-based I/O that offers direct control over buffer size. A common trap is assuming BufferedReader or memory-mapped files are always best—but for a 1 GB file, FileChannel with a direct ByteBuffer gives you predictable, low-overhead chunking. Memory tip: think “channel + chunk” to remember that FileChannel reads in controlled slices, not all at once.
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 very large text file (over 1 GB) efficiently with minimal memory overhead. Which approach is most suitable?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use FileChannel with a ByteBuffer to read in chunks.
FileChannel with a ByteBuffer allows reading a large file in configurable chunks, leveraging the operating system's native I/O for high throughput and minimal memory overhead. This approach avoids loading the entire file into memory and reduces context switching compared to stream-based readers.
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 Scanner to read tokens.
Why it's wrong here
Scanner is not designed for high-performance file reading; it's for parsing.
✗
Use BufferedReader to read lines.
Why it's wrong here
BufferedReader loads lines into memory; for large files, this can be memory-intensive.
✗
Use FileInputStream and read byte by byte.
Why it's wrong here
Reading byte by byte is extremely inefficient for large files.
✓
Use FileChannel with a ByteBuffer to read in chunks.
Why this is correct
FileChannel with ByteBuffer allows efficient chunked reading, minimizing memory usage.
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 for its simplicity, not realizing that reading lines from a multi-GB file still requires holding entire lines in memory, which can cause OutOfMemoryError or severe performance degradation.
Detailed technical explanation
How to think about this question
FileChannel uses the underlying operating system's `pread` or `readv` syscalls via native I/O, allowing direct memory mapping or chunked reads with ByteBuffer. The ByteBuffer can be allocated as direct (off-heap) to avoid copying data between Java heap and native memory, further reducing GC pressure. This pattern is ideal for processing large files where random access or streaming in fixed-size blocks is required.
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 FileChannel with a ByteBuffer to read in chunks. — FileChannel with a ByteBuffer allows reading a large file in configurable chunks, leveraging the operating system's native I/O for high throughput and minimal memory overhead. This approach avoids loading the entire file into memory and reduces context switching compared to stream-based readers.
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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