Hi, This is not very obvious and looks like a bug.
I have a lambda expression to get key from objects in stream: This works: stream.keyBy(value -> value.getId()) This does not: stream.keyBy(myClass::getId) Exception: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1 at org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:294) at org.apache.flink.api.java.typeutils.TypeExtractor.getKeySelectorTypes(TypeExtractor.java:253) at org.apache.flink.api.java.typeutils.TypeExtractor.getKeySelectorTypes(TypeExtractor.java:246) at org.apache.flink.streaming.api.datastream.KeyedStream.<init>(KeyedStream.java:87) at org.apache.flink.streaming.api.datastream.DataStream.keyBy(DataStream.java:241) Can someone confirm this? or is there a better way to do it? Thanks! Andrew -- Confidentiality Notice: This e-mail transmission may contain confidential or legally privileged information that is intended only for the individual or entity named in the e-mail address. If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution, or reliance upon the contents of this e-mail is strictly prohibited and may be unlawful. If you have received this e-mail in error, please notify the sender immediately by return e-mail and delete all copies of this message.