Bael 766 flink (#1533)

* BAEL-756 code for flink article

* reorder

* simpler wordCount example

* BAEL-766 changes according to PR

* BAEL-766 change datasource to dataset

* BAEL-766 add sorting example

* BAEL-766 add simple streaming example

* one missing change to dataSet

* windowing example

* add window example

* add dependency explicitly

* add plugin

* add surefire plugin, change neme of the test to *IntegrationTest

libraries/src/main/java/com/baeldung/flink/LineSplitter.java

@@ -0,0 +1,20 @@
+package com.baeldung.flink;
+
+import org.apache.flink.api.common.functions.FlatMapFunction;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.util.Collector;
+
+import java.util.stream.Stream;
+
+@SuppressWarnings("serial")
+public class LineSplitter implements FlatMapFunction<String, Tuple2<String, Integer>> {
+
+    @Override
+    public void flatMap(String value, Collector<Tuple2<String, Integer>> out) {
+
+        String[] tokens = value.toLowerCase().split("\\W+");
+        Stream.of(tokens)
+                .filter(t -> t.length() > 0)
+                .forEach(token -> out.collect(new Tuple2<>(token, 1)));
+    }
+}

libraries/src/main/java/com/baeldung/flink/WordCount.java

@@ -0,0 +1,20 @@
+package com.baeldung.flink;
+
+import org.apache.flink.api.java.DataSet;
+import org.apache.flink.api.java.ExecutionEnvironment;
+import org.apache.flink.api.java.aggregation.Aggregations;
+import org.apache.flink.api.java.tuple.Tuple2;
+
+import java.util.List;
+
+public class WordCount {
+
+    public static DataSet<Tuple2<String, Integer>> startWordCount(ExecutionEnvironment env, List<String> lines) throws Exception {
+        DataSet<String> text = env.fromCollection(lines);
+
+        return text.flatMap(new LineSplitter())
+                .groupBy(0)
+                .aggregate(Aggregations.SUM, 1);
+
+    }
+}