spring-projectsGH-3132: Remove usage of super();

Fixes spring-projects#3132

It turns out that Checkstyle EmptyBlock doesn't complain about
empty default ctor.
Plus a new check for `super();` call treats it as a violation

* Remove `super();` from all the no-arg ctors
* Code style clean up in the affected classes according
IDEA suggestions

Author: artembilan

spring-integration-amqp/src/main/java/org/springframework/integration/amqp/support/EndpointUtils.java

@@ -25,6 +25,7 @@
  * Utility methods for messaging endpoints.
  *
  * @author Gary Russell
+ * @author Artem Bilan
  *
  * @since 5.1.3
  *
@@ -34,7 +35,6 @@ public final class EndpointUtils {
 	private static final String LEFE_MESSAGE = "Message conversion failed";
 
 	private EndpointUtils() {
-		super();
 	}
 
 	/**
@@ -43,16 +43,16 @@ private EndpointUtils() {
 	 * @param message the failed message.
 	 * @param channel the channel.
 	 * @param isManualAck true if the container uses manual acknowledgment.
-	 * @param e the exception.
+	 * @param ex the exception.
 	 * @return the exception.
 	 */
-	public static ListenerExecutionFailedException errorMessagePayload(final Message message,
-			Channel channel, boolean isManualAck, Exception e) {
+	public static ListenerExecutionFailedException errorMessagePayload(Message message,
+			Channel channel, boolean isManualAck, Exception ex) {
 
 		return isManualAck
-				? new ManualAckListenerExecutionFailedException(LEFE_MESSAGE, e, message, channel,
+				? new ManualAckListenerExecutionFailedException(LEFE_MESSAGE, ex, message, channel,
 						message.getMessageProperties().getDeliveryTag())
-				: new ListenerExecutionFailedException(LEFE_MESSAGE, e, message);
+				: new ListenerExecutionFailedException(LEFE_MESSAGE, ex, message);
 	}
 
 }

spring-integration-amqp/src/main/java/org/springframework/integration/amqp/support/MappingUtils.java

@@ -38,7 +38,6 @@
 public final class MappingUtils {
 
 	private MappingUtils() {
-		super();
 	}
 
 	/**

spring-integration-core/src/main/java/org/springframework/integration/StaticMessageHeaderAccessor.java

@@ -31,6 +31,7 @@
  * creation just to access a header.
  *
  * @author Gary Russell
+ * @author Artem Bilan
  *
  * @since 5.0.1
  *
@@ -39,7 +40,6 @@
 public final class StaticMessageHeaderAccessor {
 
 	private StaticMessageHeaderAccessor() {
-		super();
 	}
 
 	@Nullable

spring-integration-core/src/main/java/org/springframework/integration/acks/AckUtils.java

@@ -18,31 +18,19 @@
 
 import org.springframework.integration.acks.AcknowledgmentCallback.Status;
 import org.springframework.lang.Nullable;
-import org.springframework.messaging.Message;
 
 /**
  * Utility methods for acting on {@link AcknowledgmentCallback} headers.
  *
  * @author Gary Russell
+ * @author Artem Bilan
+ *
  * @since 5.0.1
  *
  */
 public final class AckUtils {
 
 	private AckUtils() {
-		super();
-	}
-
-	/**
-	 * Return the {@link AcknowledgmentCallback} header (if present).
-	 * @param message the message.
-	 * @return the callback, or null.
-	 * @deprecated use StaticMessageHeaderAccessor.getAcknowledgmentCallback(message).
-	 */
-	@Deprecated
-	@Nullable
-	public static AcknowledgmentCallback getAckCallback(Message<?> message) {
-		throw new UnsupportedOperationException("Use StaticMessageHeaderAccessor.getAcknowledgmentCallback(message)");
 	}
 
 	/**

spring-integration-core/src/main/java/org/springframework/integration/aggregator/AbstractCorrelatingMessageHandler.java

@@ -960,7 +960,6 @@ private boolean containsSequenceNumber(Collection<Message<?>> messages, Integer
 	private class ForceReleaseMessageGroupProcessor implements MessageGroupProcessor {
 
 		ForceReleaseMessageGroupProcessor() {
-			super();
 		}
 
 		@Override

spring-integration-core/src/main/java/org/springframework/integration/aggregator/MessageCountReleaseStrategy.java

@@ -19,29 +19,30 @@
 import org.springframework.integration.store.MessageGroup;
 
 /**
- * A {@link ReleaseStrategy} that releases only the first <code>n</code> messages, where <code>n</code> is a threshold.
+ * A {@link ReleaseStrategy} that releases only the first {@code n} messages, where {@code n} is a threshold.
  *
  * @author Dave Syer
  * @author Oleg Zhurakousky
+ * @author Artem Bilan
  *
  */
 public class MessageCountReleaseStrategy implements ReleaseStrategy {
 
 	private final int threshold;
 
 	/**
-	 * @param threshold the number of messages to accept before releasing
+	 * Convenient constructor is only one message is required (threshold=1).
 	 */
-	public MessageCountReleaseStrategy(int threshold) {
-		super();
-		this.threshold = threshold;
+	public MessageCountReleaseStrategy() {
+		this(1);
 	}
 
 	/**
-	 * Convenient constructor is only one message is required (threshold=1).
+	 * Construct an instance based on the provided threshold.
+	 * @param threshold the number of messages to accept before releasing
 	 */
-	public MessageCountReleaseStrategy() {
-		this(1);
+	public MessageCountReleaseStrategy(int threshold) {
+		this.threshold = threshold;
 	}
 
 	/**

spring-integration-core/src/main/java/org/springframework/integration/channel/ChannelUtils.java

@@ -35,7 +35,6 @@ public final class ChannelUtils {
 	public static final String MESSAGE_PUBLISHING_ERROR_HANDLER_BEAN_NAME = "integrationMessagePublishingErrorHandler";
 
 	private ChannelUtils() {
-		super();
 	}
 
 	/**
@@ -56,5 +55,4 @@ public static ErrorHandler getErrorHandler(BeanFactory beanFactory) {
 		return beanFactory.getBean(MESSAGE_PUBLISHING_ERROR_HANDLER_BEAN_NAME, ErrorHandler.class);
 	}
 
-
 }

spring-integration-core/src/main/java/org/springframework/integration/channel/MessageChannelReactiveUtils.java

@@ -40,7 +40,6 @@
 public final class MessageChannelReactiveUtils {
 
 	private MessageChannelReactiveUtils() {
-		super();
 	}
 
 	@SuppressWarnings("unchecked")

spring-integration-core/src/main/java/org/springframework/integration/dsl/Channels.java

@@ -132,7 +132,6 @@ public FluxMessageChannelSpec flux(String id) {
 	}
 
 	private Channels() {
-		super();
 	}
 
 }

spring-integration-core/src/main/java/org/springframework/integration/dsl/DirectChannelSpec.java

@@ -38,7 +38,6 @@ protected DirectChannel doGet() {
 	}
 
 	DirectChannelSpec() {
-		super();
 	}
 
 }

spring-integration-core/src/main/java/org/springframework/integration/dsl/IntegrationFlowBuilder.java

@@ -28,7 +28,6 @@
 public final class IntegrationFlowBuilder extends IntegrationFlowDefinition<IntegrationFlowBuilder> {
 
 	IntegrationFlowBuilder() {
-		super();
 	}
 
 	@Override

spring-integration-core/src/main/java/org/springframework/integration/dsl/LoadBalancingChannelSpec.java

@@ -39,7 +39,6 @@ public abstract class LoadBalancingChannelSpec<S extends MessageChannelSpec<S, C
 	protected Integer maxSubscribers; // NOSONAR
 
 	protected LoadBalancingChannelSpec() {
-		super();
 	}
 
 	public S loadBalancer(LoadBalancingStrategy loadBalancingStrategyToSet) {

spring-integration-core/src/main/java/org/springframework/integration/dsl/MessageChannelSpec.java

@@ -54,7 +54,6 @@ public abstract class MessageChannelSpec<S extends MessageChannelSpec<S, C>, C e
 	private MessageConverter messageConverter;
 
 	protected MessageChannelSpec() {
-		super();
 	}
 
 	public S datatype(Class<?>... types) {
@@ -118,7 +117,7 @@ public Map<Object, String> getComponentsToRegister() {
 
 	@Override
 	protected C doGet() {
-		this.channel.setDatatypes(this.datatypes.toArray(new Class<?>[this.datatypes.size()]));
+		this.channel.setDatatypes(this.datatypes.toArray(new Class<?>[0]));
 		this.channel.setBeanName(getId());
 		this.channel.setInterceptors(this.interceptors);
 		this.channel.setMessageConverter(this.messageConverter);

spring-integration-core/src/main/java/org/springframework/integration/dsl/MessageChannels.java

@@ -133,7 +133,6 @@ public static FluxMessageChannelSpec flux(String id) {
 	}
 
 	private MessageChannels() {
-		super();
 	}
 
 }

spring-integration-core/src/main/java/org/springframework/integration/dsl/PollerFactory.java

@@ -81,7 +81,6 @@ public PollerSpec fixedDelay(long period) {
 	}
 
 	PollerFactory() {
-		super();
 	}
 
 }

spring-integration-core/src/main/java/org/springframework/integration/dsl/PriorityChannelSpec.java

@@ -38,7 +38,6 @@ public class PriorityChannelSpec extends MessageChannelSpec<PriorityChannelSpec,
 	private MessageGroupQueue messageGroupQueue;
 
 	PriorityChannelSpec() {
-		super();
 	}
 
 	public PriorityChannelSpec capacity(int capacity) {

spring-integration-core/src/main/java/org/springframework/integration/dsl/PublishSubscribeChannelSpec.java

@@ -19,6 +19,7 @@
 import java.util.concurrent.Executor;
 
 import org.springframework.integration.channel.PublishSubscribeChannel;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ErrorHandler;
 
 /**
@@ -33,10 +34,10 @@ public class PublishSubscribeChannelSpec<S extends PublishSubscribeChannelSpec<S
 		extends MessageChannelSpec<S, PublishSubscribeChannel> {
 
 	protected PublishSubscribeChannelSpec() {
-		this.channel = new PublishSubscribeChannel();
+		this(null);
 	}
 
-	protected PublishSubscribeChannelSpec(Executor executor) {
+	protected PublishSubscribeChannelSpec(@Nullable Executor executor) {
 		this.channel = new PublishSubscribeChannel(executor);
 	}
 

spring-integration-core/src/main/java/org/springframework/integration/dsl/PublishSubscribeSpec.java

@@ -20,6 +20,7 @@
 import java.util.Map;
 import java.util.concurrent.Executor;
 
+import org.springframework.lang.Nullable;
 import org.springframework.messaging.MessageChannel;
 import org.springframework.util.Assert;
 
@@ -36,10 +37,9 @@ public class PublishSubscribeSpec extends PublishSubscribeChannelSpec<PublishSub
 	private int order;
 
 	PublishSubscribeSpec() {
-		super();
 	}
 
-	PublishSubscribeSpec(Executor executor) {
+	PublishSubscribeSpec(@Nullable Executor executor) {
 		super(executor);
 	}
 

spring-integration-core/src/main/java/org/springframework/integration/dsl/QueueChannelSpec.java

@@ -36,7 +36,6 @@ public class QueueChannelSpec extends MessageChannelSpec<QueueChannelSpec, Queue
 	protected Integer capacity; // NOSONAR
 
 	QueueChannelSpec() {
-		super();
 	}
 
 	QueueChannelSpec(Queue<Message<?>> queue) {
@@ -73,7 +72,6 @@ public static class MessageStoreSpec extends QueueChannelSpec {
 		private Lock storeLock;
 
 		MessageStoreSpec(ChannelMessageStore messageGroupStore, Object groupId) {
-			super();
 			this.messageGroupStore = messageGroupStore;
 			this.groupId = groupId;
 		}

spring-integration-core/src/main/java/org/springframework/integration/endpoint/ReactiveStreamsConsumer.java

@@ -150,7 +150,6 @@ private final class DelegatingSubscriber extends BaseSubscriber<Message<?>> {
 		private final Subscriber<Message<?>> delegate = ReactiveStreamsConsumer.this.subscriber;
 
 		DelegatingSubscriber() {
-			super();
 		}
 
 		@Override

spring-integration-core/src/main/java/org/springframework/integration/expression/ExpressionEvalMap.java

@@ -303,7 +303,6 @@ public ExpressionEvalMapComponentsBuilder withReturnType(Class<?> returnType) {
 		private class ExpressionEvalMapFinalBuilderImpl implements ExpressionEvalMapFinalBuilder {
 
 			ExpressionEvalMapFinalBuilderImpl() {
-				super();
 			}
 
 			@Override
@@ -327,7 +326,6 @@ private class ExpressionEvalMapComponentsBuilderImpl extends ExpressionEvalMapFi
 				implements ExpressionEvalMapComponentsBuilder {
 
 			ExpressionEvalMapComponentsBuilderImpl() {
-				super();
 			}
 
 			@Override

spring-integration-core/src/main/java/org/springframework/integration/expression/ExpressionUtils.java

@@ -60,7 +60,6 @@ public final class ExpressionUtils {
 	private static final Log LOGGER = LogFactory.getLog(ExpressionUtils.class);
 
 	private ExpressionUtils() {
-		super();
 	}
 
 	/**