如何在Flink中连接2个以上的流？

DataStream<Integer> stream1 = ...
DataStream<Integer> stream2 = ...
DataStream<Integer> stream3 = ...

DataStream<Integer> unionStream = stream1.union(stream2, stream3);

DataStream<Integer> stream1 = ...
DataStream<String> stream2 = ...

ConnectedStreams<Integer, String> connectedStreams = stream1.connect(stream2);

DataStream<Tuple2<String, Integer>> stream1 = ...
DataStream<Tuple2<String, String>> stream2 = ...

DataStream<Tuple3<String, Integer, String>> joinedStream = stream1.join(stream2)
    .where(new KeySelector<Tuple2<String, Integer>, String>() {
        @Override
        public String getKey(Tuple2<String, Integer> value) throws Exception {
            return value.f0;
        }
    })
    .equalTo(new KeySelector<Tuple2<String, String>, String>() {
        @Override
        public String getKey(Tuple2<String, String> value) throws Exception {
            return value.f0;
        }
    })
    .window(TumblingProcessingTimeWindows.of(Time.seconds(10)))
    .apply(new JoinFunction<Tuple2<String, Integer>, Tuple2<String, String>, Tuple3<String, Integer, String>>() {
        @Override
        public Tuple3<String, Integer, String> join(Tuple2<String, Integer> first, Tuple2<String, String> second) throws Exception {
            return new Tuple3<>(first.f0, first.f1, second.f1);
        }
    });

DataStream<Integer> stream1 = ...
DataStream<Integer> stream2 = ...

DataStream<Integer> coFlatMapStream = stream1.connect(stream2)
    .flatMap(new CoFlatMapFunction<Integer, Integer, Integer>() {
        @Override
        public void flatMap1(Integer value, Collector<Integer> out) throws Exception {
            // 处理stream1的元素
            out.collect(value * 2);
        }

        @Override
        public void flatMap2(Integer value, Collector<Integer> out) throws Exception {
            // 处理stream2的元素
            out.collect(value + 1);
        }
    });