1Z0-829 Java I/O API and Securing Applications Practice Question
An application must read a configuration file that is updated frequently by another process. The developer wants to avoid stale data and minimize I/O operations. Which approach is best?
⚠ Common exam trap
Test-takers frequently choose option C (polling with lastModified) because it seems simple and avoids continuous reads, but they overlook that polling still wastes resources and may miss updates, whereas WatchService is the true event-driven solution that minimizes I/O and avoids stale data.
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
✓
Use java.nio.file.WatchService to monitor the file for modifications and reload when notified
Java.nio.file.WatchService provides an event-driven mechanism to monitor file system changes, such as modifications to a configuration file. This approach avoids stale data by reloading the file only when a change is detected, and it minimizes I/O operations by eliminating the need for polling or repeated reads. The WatchService uses the underlying OS file system events (e.g., inotify on Linux, ReadDirectoryChanges on Windows) for efficient notification.
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 java.nio.file.WatchService to monitor the file for modifications and reload when notified
Why this is correct
WatchService provides asynchronous notifications, reducing unnecessary reads and ensuring freshness.
- ✗
Read the file from disk every time it is accessed using Files.newInputStream()
Why it's wrong here
Reading on every access causes excessive I/O, especially if the file is accessed frequently.
- ✗
Periodically check the file's lastModified timestamp using File.lastModified() and reload if changed
Why it's wrong here
Polling still involves frequent I/O and timestamps may have limited granularity.
- ✗
Read the file once at startup and cache the content in memory
Why it's wrong here
This ignores updates, leading to stale data.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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