public synchronized R get() throws IOException {
    while (!resultSet) {
      try {
        this.wait();
      } catch (InterruptedException ie) {
        InterruptedIOException exception = new InterruptedIOException(ie.getMessage());
        exception.initCause(ie);
        throw exception;
      }
    }
    return result;
  }
Returns the parameter passed to {@link #run(Object)} or {@code null} if a null value was
passed. When used asynchronously, this method will block until the {@link #run(Object)} method
has been called.
@return the response object or {@code null} if no response was passed
hbase-client/src/main/java/org/apache/hadoop/hbase/client/CoprocessorBlockingRpcCallback.java