[FLINK-5360] Fix argument names in WindowedStream

Author: mushketyk

flink-streaming-java/src/main/java/org/apache/flink/streaming/api/datastream/WindowedStream.java

@@ -833,14 +833,14 @@ public SingleOutputStreamOperator<T> minBy(int positionToMinBy) {
 
 	/**
 	 * Applies an aggregation that gives the minimum element of every window of
-	 * the data stream by the given position. If more elements have the same
+	 * the data stream by the given field. If more elements have the same
 	 * minimum value the operator returns the first element by default.
 	 *
-	 * @param positionToMinBy The position to minimize by
+	 * @param field The field to minimize by
 	 * @return The transformed DataStream.
 	 */
-	public SingleOutputStreamOperator<T> minBy(String positionToMinBy) {
-		return this.minBy(positionToMinBy, true);
+	public SingleOutputStreamOperator<T> minBy(String field) {
+		return this.minBy(field, true);
 	}
 
 	/**
@@ -912,15 +912,15 @@ public SingleOutputStreamOperator<T> maxBy(int positionToMaxBy) {
 
 	/**
 	 * Applies an aggregation that gives the maximum element of every window of
-	 * the data stream by the given position. If more elements have the same
+	 * the data stream by the given field. If more elements have the same
 	 * maximum value the operator returns the first by default.
 	 *
-	 * @param positionToMaxBy
-	 *            The position to maximize by
+	 * @param field
+	 *            The field to maximize by
 	 * @return The transformed DataStream.
 	 */
-	public SingleOutputStreamOperator<T> maxBy(String positionToMaxBy) {
-		return this.maxBy(positionToMaxBy, true);
+	public SingleOutputStreamOperator<T> maxBy(String field) {
+		return this.maxBy(field, true);
 	}
 
 	/**