@Override
    public Promise<Buffer> readFile(String path) {
        return adapter.toPromise(handler -> vertx.fileSystem().readFile(path, handler));
    }
@ Override public Promise < Buffer > readFile ( String path ) { return adapter . toPromise ( handler -> vertx . fileSystem ( ) . readFile ( path , handler ) ) ; }
Reads the entire file as represented by the path {@code path} as a {@link io.vertx.core.buffer.Buffer}, asynchronously.
<p>
Do not user this method to read very large files or you risk running out of available RAM.

@param path path to the file
@return a promise for the file data