How does WatchService (file watchers) behave in multithreaded code?

WatchService is part of the Java NIO (New Input/Output) package, which provides a way to monitor changes in files and directories in a filesystem. When used in multithreaded code, there are some important behaviors and considerations to keep in mind:

• Thread Safety: The WatchService itself is not inherently thread-safe. If multiple threads are accessing the same WatchService instance, synchronization mechanisms should be used to avoid race conditions.
• Callback Handling: When a file change event is detected, it is crucial to handle the event correctly, especially in a multithreaded environment. You may want to use a thread pool or a dedicated handler thread to process these events.
• Event Queue: The events are pushed into a queue that is processed in the order they are received. Ensure that your processing logic is capable of handling events in a timely manner without blocking other operations.
• Resource Management: Always ensure proper resource management (like closing WatchService) in a multithreaded context to prevent resource leaks.