1Z0-829 Java I/O API and Securing Applications Practice Question
A Java application writes sensitive user data to a file. To ensure that data is not left in the file system after the application crashes, which practice should be followed?
⚠ Common exam trap
A common mix-up: candidates confuse data flushing or locking with crash-safe file updates, but neither `flush()` nor `FileLock` provides atomicity guarantees, which is the key requirement for preventing data corruption after a crash.
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
✓
Write to a temporary file, then use Files.move() with ATOMIC_MOVE to replace the target file
Writing to a temporary file and then atomically moving it with `Files.move()` using the `ATOMIC_MOVE` option ensures that the target file is replaced only after the write succeeds. If the application crashes during the write, only the temporary file is corrupted, and the original target file remains intact. This prevents sensitive data from being left in an incomplete or partially written state in the file system.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Call flush() after every write operation
Why it's wrong here
Flush only ensures data is sent to the OS, but doesn't guarantee atomicity or cleanup on crash.
- ✗
Delete the file manually in a finally block
Why it's wrong here
If the JVM crashes abruptly, the finally block may not execute, leaving the file.
- ✗
Use a FileLock to prevent concurrent access
Why it's wrong here
FileLock prevents concurrent access but does not prevent data residue after a crash.
- ✓
Write to a temporary file, then use Files.move() with ATOMIC_MOVE to replace the target file
Why this is correct
Atomic move ensures the target file is either fully written or not replaced, preventing partial writes.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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