Spark Streaming：updateStateByKey報錯 is not applicable for the arguments...

ones.updateStateByKey(new Function2<List<Integer>, Optional<Integer>, Optional<Integer>>() {
            @Override
            public Optional<Integer> call(List<Integer> arg0, Optional<Integer> arg1) throws Exception {
                // TODO Auto-generated method stub
                return null;
            }
        });

對JavaPairDStream<String, Integer> ones使用updateStateByKey報錯：

The method updateStateByKey(Function2<List<Integer>,Optional<S>,Optional<S>>) in the type JavaPairDStream<String,Integer> is not applicable for the arguments (new Function2<List<Integer>,Optional<Integer>,Optional<Integer>>(){})

 

解決辦法：很可能是Optional導包導錯了，要導com.google.common.base.Optional