flink KafkaIOExamples submit error

I change all the beam pom.xml scala to 2.11.8,scala lib to 2.11，compile the beam jars。

Submit KafkaIOExamples in runners/FlinkRunner/KafkaIOExamples to flink,main class "ReadStringFromKafka"
error occured as follow：
org.apache.flink.client.program.ProgramInvocationException: The main method caused an error.
at org.apache.flink.client.program.PackagedProgram.callMainMethod(PackagedProgram.java:524)
at org.apache.flink.client.program.PackagedProgram.invokeInteractiveModeForExecution(PackagedProgram.java:403)
at org.apache.flink.client.program.OptimizerPlanEnvironment.getOptimizedPlan(OptimizerPlanEnvironment.java:80)
at org.apache.flink.client.program.ClusterClient.getOptimizedPlan(ClusterClient.java:274)
at org.apache.flink.runtime.webmonitor.handlers.JarActionHandler.getJobGraphAndClassLoader(JarActionHandler.java:95)
at org.apache.flink.runtime.webmonitor.handlers.JarPlanHandler.handleRequest(JarPlanHandler.java:42)
at org.apache.flink.runtime.webmonitor.RuntimeMonitorHandler.respondAsLeader(RuntimeMonitorHandler.java:88)
at org.apache.flink.runtime.webmonitor.RuntimeMonitorHandlerBase.channelRead0(RuntimeMonitorHandlerBase.java:84)
at org.apache.flink.runtime.webmonitor.RuntimeMonitorHandlerBase.channelRead0(RuntimeMonitorHandlerBase.java:44)
at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:339)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:324)
at io.netty.handler.codec.http.router.Handler.routed(Handler.java:62)
at io.netty.handler.codec.http.router.DualAbstractHandler.channelRead0(DualAbstractHandler.java:57)
at io.netty.handler.codec.http.router.DualAbstractHandler.channelRead0(DualAbstractHandler.java:20)
at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:339)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:324)
at org.apache.flink.runtime.webmonitor.HttpRequestHandler.channelRead0(HttpRequestHandler.java:105)
at org.apache.flink.runtime.webmonitor.HttpRequestHandler.channelRead0(HttpRequestHandler.java:65)
at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:339)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:324)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:242)
at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:147)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:339)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:324)
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:847)
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:131)
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:511)
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:468)
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:382)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354)
at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:111)
at io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:137)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalStateException: null
at org.apache.beam.sdk.repackaged.com.google.common.base.Preconditions.checkState(Preconditions.java:174)
at org.apache.beam.sdk.values.TypedPValue.getCoder(TypedPValue.java:51)
at org.apache.beam.sdk.values.PCollection.getCoder(PCollection.java:130)
at org.apache.beam.sdk.values.TypedPValue.finishSpecifying(TypedPValue.java:90)
at org.apache.beam.sdk.runners.TransformHierarchy.finishSpecifyingInput(TransformHierarchy.java:95)
at org.apache.beam.sdk.Pipeline.applyInternal(Pipeline.java:386)
at org.apache.beam.sdk.Pipeline.applyTransform(Pipeline.java:302)
at org.apache.beam.sdk.values.PCollection.apply(PCollection.java:154)
at com.xdata.beam.wordcount.KafkaIOExamples$KafkaString$ReadStringFromKafka.main(KafkaIOExamples.java:83)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at org.apache.flink.client.program.PackagedProgram.callMainMethod(PackagedProgram.java:509)
... 35 more