The correct choice is to use FileOutputStream and call flush() after each write because this approach provides direct, unbuffered byte-level access to the underlying file, forcing the operating system to perform an immediate disk write for each log entry. When you call flush() on a FileOutputStream, it bypasses any intermediate buffering layers that could otherwise hold data in memory, ensuring that the log data is persisted to disk even if the JVM crashes before the next write cycle. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this question tests your understanding of I/O stream buffering behavior and the critical distinction between flushing a stream and closing it—a common trap is assuming that BufferedWriter or PrintWriter with autoFlush provides the same guarantee, but those classes still buffer internally before reaching the OS. Remember the memory tip: "Flush is a must for crash-proof disk trust"—without an explicit flush, data can remain in a buffer and be lost on a crash.
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. Compare every option against the stated constraints before choosing — the best answer satisfies all requirements, not just the most obvious one. 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 web server application writes access logs to a file. To ensure that log entries are written to disk immediately even if the JVM crashes, which approach is most appropriate?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "immediately / without restart"
Why it matters: Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use FileOutputStream and call flush() after each write.
Option A is correct because FileOutputStream provides direct, unbuffered byte-level access to the underlying file. Calling flush() after each write forces the operating system to immediately write the data to disk, ensuring that log entries are persisted even if the JVM crashes before the next write cycle. This approach bypasses any intermediate buffering that could lose data.
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 FileOutputStream and call flush() after each write.
Why this is correct
Flushing after each write forces the data to be written to the underlying file system.
Clue confirmation
The clue word "immediately / without restart" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use BufferedWriter and call write() then flush() periodically.
Why it's wrong here
BufferedWriter may still buffer if not flushed after each write; periodic flush is not immediate.
✗
Use PrintWriter with autoFlush enabled.
Why it's wrong here
autoFlush only flushes on newline, not on every write.
✗
Use FileWriter without any buffering.
Why it's wrong here
FileWriter may be buffered by the underlying system; flush still needed.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'flush()' with 'sync()' and assume that flushing a buffered stream (like BufferedWriter or PrintWriter) guarantees disk persistence, when in fact it only pushes data to the next layer (e.g., OS buffer) and does not ensure an immediate disk write.
Detailed technical explanation
How to think about this question
Under the hood, FileOutputStream.write() calls the native write system call (e.g., write() on POSIX or WriteFile() on Windows), which transfers data to the OS page cache. Calling flush() on a FileOutputStream does nothing by default (it is a no-op), but the key point is that FileOutputStream itself does not buffer; the OS may still cache the data, but the data is in kernel space and will be written to disk unless the OS crashes. For guaranteed immediate disk write, one would need to use FileChannel.force(true) or RandomAccessFile.getFD().sync(), which issue an fsync() system call. The exam expects that FileOutputStream with flush() is the most appropriate among the given options for immediate writing, as it avoids Java-level buffering.
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
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 FileOutputStream and call flush() after each write. — Option A is correct because FileOutputStream provides direct, unbuffered byte-level access to the underlying file. Calling flush() after each write forces the operating system to immediately write the data to disk, ensuring that log entries are persisted even if the JVM crashes before the next write cycle. This approach bypasses any intermediate buffering that could lose data.
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.
Are there clue words in this question I should notice?
Yes — watch for: "immediately / without restart". Time or reboot constraint — the correct answer must take effect right away without requiring a reboot or reload.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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