java.nio.channels.AsynchronousChannel提供了异步写文件方法，

具体代码如下：

public static void syncWrite(String path){
    File file = new File(path+"warn.log");
            if(!file.exists()) {
                file.createNewFile();
            }
            Path pathSyn = Paths.get(path+line+"warn.log");
            try {
                AsynchronousFileChannel channel = AsynchronousFileChannel.open(pathSyn, StandardOpenOption.WRITE);
                ByteBuffer buffer = ByteBuffer.allocate(1024);
                buffer = ByteBuffer.wrap(clientSender.getBytes("utf-8"));
                Future<Integer> future = channel.write(buffer, channel.size());
                channel.force(true);
                while (!future.isDone());
                buffer.clear();
                channel.close();
            } catch (Exception e) {
                e.printStackTrace();
            }    
}

异步NIO写文件