flink The object probably contains or references non serializable fields.

Exception in thread "main" org.apache.flink.api.common.InvalidProgramException: java.lang.ref.ReferenceQueue$Lock@11fc564b is not serializable. The object probably contains or references non serializable fields.at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:151)at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:126)at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:126)at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:126)at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:126)at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:126)at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:71)at org.apache.flink.streaming.api.environment.StreamExecutionEnvironment.clean(StreamExecutionEnvironment.java:1821)at org.apache.flink.streaming.api.datastream.DataStream.clean(DataStream.java:188)at org.apache.flink.streaming.api.datastream.KeyedStream.process(KeyedStream.java:398)at org.apache.flink.streaming.api.datastream.KeyedStream.process(KeyedStream.java:374)at com.xintujing.flinkdemo.text.UserCount_3.main(UserCount_3.java:53)Caused by: java.io.NotSerializableException: java.lang.ref.ReferenceQueue$Lockat java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)at org.apache.flink.util.InstantiationUtil.serializeObject(InstantiationUtil.java:586)at org.apache.flink.api.java.ClosureCleaner.clean(ClosureCleaner.java:133)... 11 more

transient