The correct answer is to use a PrintWriter wrapping a FileWriter with autoFlush set to true. This works because PrintWriter’s autoFlush mechanism triggers an immediate flush of the underlying stream every time a println, printf, or format method is called, ensuring that log messages are written to disk without delay. The FileWriter’s internal buffer still aggregates small writes for performance, but autoFlush guarantees that data is not lost during a crash. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this question tests your understanding of Java I/O buffering and the specific contract of PrintWriter’s autoFlush flag—a common trap is confusing it with BufferedWriter’s flush behavior. Remember the mnemonic: “PrintWriter’s autoFlush is your crash-proof crush.”
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 logging framework in Java has been writing logs to a file using a FileWriter with default buffer size. The logs are frequently lost when the application crashes because the buffer is not flushed. Which change ensures that log messages are written immediately without significantly impacting performance?
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 a PrintWriter wrapping a FileWriter and set autoFlush=true.
Option C is correct because a PrintWriter wrapping a FileWriter with autoFlush=true ensures that every println, printf, or format call triggers an automatic flush of the underlying stream. This guarantees log messages are written to disk immediately upon each write, preventing data loss during a crash, while still allowing the FileWriter's internal buffer to aggregate small writes for performance. The autoFlush mechanism in PrintWriter is specifically designed for this use case in Java I/O.
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 FileWriter with autoFlush=true.
Why it's wrong here
FileWriter does not have an autoFlush constructor; this option is invalid.
✗
Set the buffer size to 0 to disable buffering.
Why it's wrong here
Disabling buffering results in a system call per write, severely impacting performance.
✓
Use a PrintWriter wrapping a FileWriter and set autoFlush=true.
Why this is correct
PrintWriter with autoFlush provides a balance: messages are flushed after each line, reducing data loss without excessive overhead.
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.
✗
Call flush() after every log message.
Why it's wrong here
Explicit flush after each message is similar to disabling buffering; high overhead.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse FileWriter's lack of an autoFlush option with PrintWriter's autoFlush feature, or they incorrectly assume that disabling buffering (buffer size 0) is a practical solution, when in fact it causes severe performance degradation due to excessive system calls.
Trap categories for this question
Similar concept trap
Explicit flush after each message is similar to disabling buffering; high overhead.
Detailed technical explanation
How to think about this question
Under the hood, PrintWriter with autoFlush=true works by checking a boolean flag after each println, printf, or format call; if true, it invokes the underlying Writer's flush() method, which in turn calls the FileWriter's internal stream's flush, ultimately writing the buffered data to the OS file system. A subtle behavior is that autoFlush only triggers on newline-terminated writes (println) or format methods, not on plain write() calls—so developers must use println or printf for guaranteed immediate writes. In real-world logging frameworks like java.util.logging or Log4j, this pattern is often replaced by more sophisticated appenders with configurable flush policies, but for simple file logging, PrintWriter with autoFlush remains a lightweight solution.
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 a PrintWriter wrapping a FileWriter and set autoFlush=true. — Option C is correct because a PrintWriter wrapping a FileWriter with autoFlush=true ensures that every println, printf, or format call triggers an automatic flush of the underlying stream. This guarantees log messages are written to disk immediately upon each write, preventing data loss during a crash, while still allowing the FileWriter's internal buffer to aggregate small writes for performance. The autoFlush mechanism in PrintWriter is specifically designed for this use case in Java I/O.
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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