Apache Flink：运营商状态检查点

"我想使用Operator State APIin No-Keyed Stream来保存count下面示例中的状态。我该怎么办？

public static class MapFunction implements MapFunction,CheckpointedFunction{

int count = 0;
@Override
public String map(String value) throws Exception {
    // TODO Auto-generated method stub
        String message;
        message = value;
        count++;
        return message;
}

@Override
public void snapshotState(FunctionSnapshotContext context) throws Exception {
    // TODO Auto-generated method stub
}

@Override
public void initializeState(FunctionInitializationContext context) throws Exception {
    // TODO Auto-generated method stub
}

}"