Exception in thread "application-name" java.lang.NullPointerException at com.company.name.kafka.streams.ReduceStreamApp.subtractCounts(ReduceStreamApp.java:100) at org.apache.kafka.streams.kstream.internals.KTableReduce$KTableReduceProcessor.process(KTableReduce.java:86) at org.apache.kafka.streams.kstream.internals.KTableReduce$KTableReduceProcessor.process(KTableReduce.java:50) at org.apache.kafka.streams.processor.internals.ProcessorNode$1.run(ProcessorNode.java:46) at org.apache.kafka.streams.processor.internals.StreamsMetricsImpl.measureLatencyNs(StreamsMetricsImpl.java:208) at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:124) at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:85) at org.apache.kafka.streams.processor.internals.SourceNode.process(SourceNode.java:80) at org.apache.kafka.streams.processor.internals.StreamTask.process(StreamTask.java:216) at org.apache.kafka.streams.processor.internals.AssignedTasks.process(AssignedTasks.java:403) at org.apache.kafka.streams.processor.internals.TaskManager.process(TaskManager.java:317) at org.apache.kafka.streams.processor.internals.StreamThread.processAndMaybeCommit(StreamThread.java:942) at org.apache.kafka.streams.processor.internals.StreamThread.runOnce(StreamThread.java:822) at org.apache.kafka.streams.processor.internals.StreamThread.runLoop(StreamThread.java:774) at org.apache.kafka.streams.processor.internals.StreamThread.run(StreamThread.java:744)