找不到或无法加载主类

  StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        DataStreamSource<String> lines = env.socketTextStream("localhost", 8888);
        SingleOutputStreamOperator<Tuple2<String, Integer>> wordAndOne = lines.map(new MapFunction<String, Tuple2<String, Integer>>() {
            @Override
            public Tuple2<String, Integer> map(String value) throws Exception {
                String[] fields = value.split(",");
                return Tuple2.of(fields[0], Integer.parseInt(fields[1]));
            }
        });
        KeyedStream<Tuple2<String, Integer>, Tuple> keyBy = wordAndOne.keyBy(0);
        SingleOutputStreamOperator<Tuple2<String, Integer>> max = keyBy.max(1);
        max.print();
        env.execute();

解决：
检查target发现没有这个类

使用maven先clean再package
运行成功