DataStream<MyClass> stream1 = ...
DataStream<MyClass> stream2 = ...
DataStream<MyClass> union = stream1.union(stream2);

DataStream<Input1> stream1 = ...;
DataStream<Input2> stream2 = ...;
ConnectedStreams<Input1, Input2> connected = 
	stream1.connect(stream2);

connected.process(
	new CoProcessFunction<Input1, Input2, Output>() {
	    @Override
	    public void processElement1(
	    	Input1 input1, 
	    	CoProcessFunction<Input1, Input2, Output>.Context context,
	    	Collector<Output> collector) throws Exception {
	    		...
	    }

	    @Override
	    public void processElement2(
	    	Input2 input2, 
	    	CoProcessFunction<Input1, Input2, Output>.Context context,
	    	Collector<Output> collector) throws Exception {
				...
		}
	}
)

connected.map(
	new CoMapFunction<Input1, Input2, Output>() {
		... 
	}
)

connected.flatMap(
	new CoFlatMapFunction<Input1, Input2, Output>() {
		...
	}
)

DataStream<MyClass> filter1 = stream.filter(...);
DataStream<MyClass> filter2 = stream.filter(...);
DataStream<MyClass> map = filter1.map(...);
DataStream<MyClass> union = map.union(filter2);

final OutputTag<Output2> outputTag = new OutputTag<Output2>("output2-id"){};

public void processElement(
	Input value,
	Context context,
	Collector<Output1> collector) {
		collector.collect(new Output1(value));
		context.output(
			outputTag, 
			new Output2(value)
		);
	}

SingleOutputStreamOperator<Output1> mainDataStream = ...;

DataStream<Output2> sideOutputStream = mainDataStream.getSideOutput(outputTag);