[Java] WatchService Examples to get file and directory change event in Java

1. Get File/Directory change event with WatchService example

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import java.io.File; import java.io.IOException; import java.nio.file.FileSystems; import java.nio.file.Path; import java.nio.file.StandardWatchEventKinds; import java.nio.file.WatchEvent; import java.nio.file.WatchEvent.Kind; import java.nio.file.WatchKey; import java.nio.file.WatchService; import java.util.Arrays; public class Watcher { WatchService watcher; WatchKey watchKey; String folder; Watcher(String folder) throws IOException { this.folder = folder; this.watcher = FileSystems.getDefault().newWatchService(); java.nio.file.Paths.get(folder).register(watcher, StandardWatchEventKinds.ENTRY_CREATE); } Watcher(String folder, boolean create, boolean delete, boolean modity) throws IOException { this.folder = folder; this.watcher = FileSystems.getDefault().newWatchService(); int i = 0; Kind[] kinds = new Kind[3]; if( create ) { kinds[i++] = StandardWatchEventKinds.ENTRY_CREATE; } if( delete ) { kinds[i++] = StandardWatchEventKinds.ENTRY_DELETE; } if( modity ) { kinds[i++] = StandardWatchEventKinds.ENTRY_MODIFY; } java.nio.file.Paths.get(folder).register(watcher, Arrays.copyOf(kinds,i)); } public void loop() { while( true ) { try { watchKey = watcher.take(); for (final WatchEvent event : watchKey.pollEvents()) { final WatchEvent.Kind kind = event.kind(); final Path changed = (Path) event.context(); File f = new File( folder, changed.toFile().getPath() ); System.out.println(f.getPath() + ":" + kind); } boolean valid = watchKey.reset(); if( !valid ) { System.out.println("Watch Key has been reset..."); } } catch (InterruptedException e) { } } } public static void main(String[] args) { try { Watcher w = new Watcher("D:/Temp",true,true,true); w.loop(); } catch (IOException e) { e.printStackTrace(); } } }

Result:

D:\Temp\jsch-0.1.54.zip:ENTRY_CREATE
D:\Temp\jsch-0.1.54.zip:ENTRY_MODIFY
D:\Temp\jsch-0.1.54.zip:ENTRY_MODIFY
D:\Temp\one-ftpserver-master.zip:ENTRY_CREATE
D:\Temp\one-ftpserver-master.zip:ENTRY_MODIFY
D:\Temp\jsch-0.1.54.zip:ENTRY_DELETE
D:\Temp\one-ftpserver-master.zip:ENTRY_DELETE