Flink: How to convert the deprecated fold to aggregrate?

I am following the quick start example of Flink: Monitoring the Wikipedia Edit Stream.

The example is in Java, and I am implementing it in Scala, as following:

/**
 * Wikipedia Edit Monitoring
 */
object WikipediaEditMonitoring {
  def main(args: Array[String]) {
    // set up the execution environment
    val env: StreamExecutionEnvironment = StreamExecutionEnvironment.getExecutionEnvironment

    val edits: DataStream[WikipediaEditEvent] = env.addSource(new WikipediaEditsSource)

    val result = edits.keyBy( _.getUser )
      .timeWindow(Time.seconds(5))
      .fold(("", 0L)) {
        (acc: (String, Long), event: WikipediaEditEvent) => {
          (event.getUser, acc._2 + event.getByteDiff)
        }
      }

    result.print

    // execute program
    env.execute("Wikipedia Edit Monitoring")
  }
}

However, the fold function in Flink is already deprecated, and the aggregate function is recommended.

But I did not find the example or tutorial about how to convert the deprecated fold to aggregrate.

Any idea how to do this? Probably not only by applying aggregrate.

UPDATE

I have another implementation as following:

/**
 * Wikipedia Edit Monitoring
 */
object WikipediaEditMonitoring {
  def main(args: Array[String]) {
    // set up the execution environment
    val env: StreamExecutionEnvironment = StreamExecutionEnvironment.getExecutionEnvironment

    val edits: DataStream[WikipediaEditEvent] = env.addSource(new WikipediaEditsSource)

    val result = edits
      .map( e => UserWithEdits(e.getUser, e.getByteDiff) )
      .keyBy( "user" )
      .timeWindow(Time.seconds(5))
      .sum("edits")

    result.print

    // execute program
    env.execute("Wikipedia Edit Monitoring")
  }

  /** Data type for words with count */
  case class UserWithEdits(user: String, edits: Long)
}

I also would like to know how to have the implementation using self-defined AggregateFunction.

UPDATE

I followed this documentation: AggregateFunction, but have the following question:

In the source code of Interface AggregateFunction for release 1.3, you will see add indeed returns void:

void add(IN value, ACC accumulator);

But for version 1.4 AggregateFunction, is is returning:

ACC add(IN value, ACC accumulator);

How should I handle this?

The Flink version I am using is 1.3.2 and the documentation for this version is not having AggregateFunction, but there is no release 1.4 in artifactory yet.