flink中使用java 8 lambda编程报错:Caused by: org.apache.flink.api.common.functions.InvalidTypesException
org.apache.flink.api.common.functions.InvalidTypesException:Thereturntypeoffunction'main(KeyStateDemo.java:23)'couldnotbedeterminedautomatically,duetotypeerasure.Youcangivetypeinformationhintsb