watchservice可以将许多事件一起发送给您，甚至可以为同一个文件提供“创建然后修改”事件，或者为正在其他地方写入的文件提供“删除”、“创建”、“修改”所有相同的事件列表（如文本编辑器重写）。
防止中间进程写入和报告的最简单方法是等待watch服务暂停。你的逻辑需要 ws.take() 用于第一个查询，然后 ws.poll(1) 如果您已经收到事件：

WatchKey wk = hasPending ? ws.poll(1,TimeUnit.MILLISECONDS) : ws.take();

这是来自一个测试程序的片段，它整理所有事件，并在最后一个程序没有返回监视结果时对它们执行操作 poll(1) .

Set<Path> created = new LinkedHashSet<>();
Set<Path> modified = new LinkedHashSet<>();
Set<Path> deleted = new LinkedHashSet<>();

while(appIsRunning) {
    boolean hasPending = created.size() + modified.size() + deleted.size() > 0;
    WatchKey wk = hasPending ? ws.poll(100,TimeUnit.MILLISECONDS) : ws.take();

    if (wk != null)  {
        for (WatchEvent<?> event : wk.pollEvents()) {
             Path parent = (Path) wk.watchable();
             Path eventPath = (Path) event.context();
             store(event.kind(), parent.resolve(eventPath), created, modified, deleted);
         }
         boolean valid = wk.reset();
         if (!valid) {
             throw new RuntimeException("Check the path, it may be deleted: "+dir);
         }
    }

    System.out.println("PENDING: cre="+created.size()+" mod="+modified.size()+" del="+deleted.size());

    // ONLY HANDLE EVENTS IF NOTHING WAS RECEIVED:
    if (wk == null && hasPending) {
        // FIRE EVENTS for each list HERE: deleted, created, modified

        // reset the list for next take() cycle:
        deleted.clear();  created.clear(); modified.clear();
    }
}

如果你只是在捕捉事件 store() 很简单，此版本将多种类型整理为最新类型：

/**
 * Save event for later processing by event kind EXCEPT for:
 * <li>DELETE followed by CREATE           => store as MODIFY
 * <li>CREATE followed by MODIFY           => store as CREATE
 * <li>CREATE or MODIFY followed by DELETE => store as DELETE
 */
private static void
store(Kind<?> kind, Path path, Set<Path> created, Set<Path> modified, Set<Path> deleted) {
    System.out.println("STORE "+kind+" path:"+path);

    boolean cre = false;
    boolean mod = false;
    boolean del = kind == StandardWatchEventKinds.ENTRY_DELETE;

    if (kind == StandardWatchEventKinds.ENTRY_CREATE) {
        mod = deleted.contains(path);
        cre = !mod;
    }
    else if (kind == StandardWatchEventKinds.ENTRY_MODIFY) {
        cre = created.contains(path);
        mod = !cre;
    }
    addOrRemove(created,  cre, path);
    addOrRemove(modified, mod, path);
    addOrRemove(deleted,  del, path);
}

// Add or remove from the set:
private static void addOrRemove(Set<Path> set, boolean add, Path path) {
    if (add) set.add(path);
    else     set.remove(path);
}

这降低了create的事件处理程序与写入操作冲突或错过文件结尾的可能性。