java.lang.IllegalArgumentException: Can not set java.lang.Long field RandomSummer$CustomLong.number to RandomSummer$CustomLong
	at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
	at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
	at sun.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:58)
	at sun.reflect.UnsafeObjectFieldAccessorImpl.get(UnsafeObjectFieldAccessorImpl.java:36)
	at java.lang.reflect.Field.get(Field.java:393)
	at org.apache.flink.api.java.typeutils.runtime.PojoSerializer.serialize(PojoSerializer.java:201)
	at org.apache.flink.runtime.plugable.SerializationDelegate.write(SerializationDelegate.java:51)
	at org.apache.flink.runtime.io.network.serialization.SpanningRecordSerializer.addRecord(SpanningRecordSerializer.java:76)
	at org.apache.flink.runtime.io.network.api.RecordWriter.emit(RecordWriter.java:82)
	at org.apache.flink.runtime.operators.shipping.OutputCollector.collect(OutputCollector.java:88)
	at org.apache.flink.runtime.operators.AllReduceDriver.run(AllReduceDriver.java:119)
	at org.apache.flink.runtime.operators.RegularPactTask.run(RegularPactTask.java:493)
	at org.apache.flink.runtime.operators.RegularPactTask.invoke(RegularPactTask.java:360)
	at org.apache.flink.runtime.execution.RuntimeEnvironment.run(RuntimeEnvironment.java:257)
	at java.lang.Thread.run(Thread.java:745)