Suppress and fix PMD/Spotbugs warnings

theodolite-benchmarks/beam-commons/src/main/java/theodolite/commons/beam/AbstractPipeline.java

@@ -12,8 +12,8 @@ import org.apache.kafka.clients.consumer.ConsumerConfig;
  */
 public class AbstractPipeline extends Pipeline {
 
-  private static final String KAFKA_CONFIG_SPECIFIC_AVRO_READER = "specific.avro.reader";
-  private static final String KAFKA_CONFIG_SCHEMA_REGISTRY_URL = "schema.registry.url";
+  private static final String KAFKA_CONFIG_SPECIFIC_AVRO_READER = "specific.avro.reader"; // NOPMD
+  private static final String KAFKA_CONFIG_SCHEMA_REGISTRY_URL = "schema.registry.url"; // NOPMD
   protected final String inputTopic;
   protected final String bootstrapServer;
   // Application Configurations

theodolite-benchmarks/uc4-beam/src/main/java/serialization/AggregatedActivePowerRecordCoder.java

@@ -44,7 +44,7 @@ public class AggregatedActivePowerRecordCoder extends Coder<AggregatedActivePowe
 
   @Override
   public List<? extends Coder<?>> getCoderArguments() {
-    return null;
+    return List.of();
   }
 
   @Override