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Aljoscha Krettek commented on FLINK-3138: ----------------------------------------- How does this manifest? I changed the WordCount (streaming) example in {{flink-java8}} to this and it still works: {code} public class WordCount { // ************************************************************************* // PROGRAM // ************************************************************************* public static String keyIt(Tuple2<String, Integer> e) { return e.f0; } public static void main(String[] args) throws Exception { if(!parseParameters(args)) { return; } // set up the execution environment final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment(); // get input data DataStream<String> text = getTextDataStream(env); DataStream<Tuple2<String, Integer>> counts = // normalize and split each line text.map(line -> line.toLowerCase().split("\\W+")).returns(String[].class) // convert splitted line in pairs (2-tuples) containing: (word,1) .flatMap((String[] tokens, Collector<Tuple2<String, Integer>> out) -> { // emit the pairs with non-zero-length words Arrays.stream(tokens) .filter(t -> t.length() > 0) .forEach(t -> out.collect(new Tuple2<>(t, 1))); }).returns("Tuple2<String, Integer>") // group by the tuple field "0" and sum up tuple field "1" .keyBy(WordCount::keyIt) .sum(1); // emit result if(fileOutput) { counts.writeAsCsv(outputPath, 1); } else { counts.print(); } // execute program env.execute("Streaming WordCount Example"); } // ************************************************************************* // UTIL METHODS // ************************************************************************* private static boolean fileOutput = false; private static String textPath; private static String outputPath; private static boolean parseParameters(String[] args) { if(args.length > 0) { // parse input arguments fileOutput = true; if(args.length == 2) { textPath = args[0]; outputPath = args[1]; } else { System.err.println("Usage: WordCount <text path> <result path>"); return false; } } else { System.out.println("Executing WordCount example with built-in default data."); System.out.println(" Provide parameters to read input data from a file."); System.out.println(" Usage: WordCount <text path> <result path>"); } return true; } private static DataStream<String> getTextDataStream(StreamExecutionEnvironment env) { if (fileOutput) { // read the text file from given input path return env.readTextFile(textPath); } else { // get default test text data return env.fromElements(WordCountData.WORDS); } } } {code} > Method References are not supported as lambda expressions > --------------------------------------------------------- > > Key: FLINK-3138 > URL: https://issues.apache.org/jira/browse/FLINK-3138 > Project: Flink > Issue Type: Bug > Components: Core > Affects Versions: 0.10.2 > Reporter: Stephan Ewen > Fix For: 1.0.0 > > > For many functions (here for example KeySelectors), one can use lambda > expressions: > {code} > DataStream<MyType> stream = ...; > stream.keyBy( v -> v.getId() ) > {code} > Java's other syntax for this, Method References, do not work: > {code} > DataStream<MyType> stream = ...; > stream.keyBy( MyType::getId ) > {code} -- This message was sent by Atlassian JIRA (v6.3.4#6332)