Use constructors in all classes to avoid Java warnings (#12302)

Signed-off-by: Jakub Scholz <www@scholzj.com>

Author: scholzj

.checkstyle/checkstyle.xml

@@ -72,6 +72,9 @@
         <module name="StaticVariableName"/>
         <module name="TypeName"/>
         <module name="AvoidStarImport"/>
+        <module name="HideUtilityClassConstructor"/>
+        <module name="MissingCtor"/>
+
 
         <!-- dependencies and import control -->
         <module name="ImportControl">

.checkstyle/suppressions.xml

@@ -33,14 +33,24 @@
     <suppress checks="UnnecessaryParentheses"
               files="io[/\\]strimzi[/\\].*"/>
 
-    <!-- Skip Javadoc checks for tests-->
+    <!-- Skip Javadoc checks for tests -->
     <suppress checks="(JavadocMethod|JavadocType|JavadocVariable|MissingJavadocType|MissingJavadocMethod)" files="src[/\\]test[/\\]java[/\\].*"/>
 
-    <!-- The api module is currently not ready or Javadoc checks-->
+    <!-- Do not require constructors in test classes -->
+    <suppress checks="(MissingCtor|HideUtilityClassConstructor)" files="src[/\\]test[/\\]java[/\\].*"/>
+
+    <!-- The api module is currently not ready for Javadoc checks -->
     <suppress checks="(JavadocMethod|JavadocType|JavadocVariable|MissingJavadocType|MissingJavadocMethod)" files="api[/\\]src[/\\]main[/\\]java[/\\]io[/\\]strimzi[/\\].*"/>
 
-    <!-- The systemtest module is currently not ready or Javadoc checks-->
+    <!-- The api module is currently not ready for constructor checks -->
+    <suppress checks="(MissingCtor|HideUtilityClassConstructor)" files="api[/\\]src[/\\]main[/\\]java[/\\]io[/\\]strimzi[/\\].*"/>
+
+    <!-- The systemtest module is currently not ready for Javadoc checks -->
     <suppress checks="(JavadocMethod|JavadocType|JavadocVariable|MissingJavadocType|MissingJavadocMethod|JavadocStyle)" files="systemtest[/\\]src[/\\]main[/\\]java[/\\]io[/\\]strimzi[/\\].*"/>
     <suppress checks="(JavadocStyle)" files="systemtest[/\\]src[/\\]test[/\\]java[/\\]io[/\\]strimzi[/\\].*"/>
 
+    <!-- The systemtest module is currently not ready for Constructor checks-->
+    <suppress checks="(MissingCtor|HideUtilityClassConstructor)" files="systemtest[/\\]src[/\\]main[/\\]java[/\\]io[/\\]strimzi[/\\].*"/>
+    <suppress checks="(MissingCtor|HideUtilityClassConstructor)" files="systemtest[/\\]src[/\\]test[/\\]java[/\\]io[/\\]strimzi[/\\].*"/>
+
 </suppressions>

api/src/main/java/io/strimzi/api/ResourceAnnotations.java

@@ -7,7 +7,13 @@
 /**
  * Class for holding some annotation keys.
  */
+@SuppressWarnings("HideUtilityClassConstructor") // We extend this class latest in the CO module, that is why it cannot have a private constructor
 public class ResourceAnnotations {
+    /**
+     * Constructor
+     */
+    public ResourceAnnotations() { }
+
     /**
      * The Strimzi domain used in all annotations
      */

api/src/main/java/io/strimzi/api/ResourceLabels.java

@@ -7,7 +7,13 @@
 /**
  * An immutable set of labels
  */
+@SuppressWarnings("HideUtilityClassConstructor") // We extend this class latest in the CO module, that is why it cannot have a private constructor
 public class ResourceLabels {
+    /**
+     * Constructor
+     */
+    public ResourceLabels() { }
+
     /**
      * Strimzi domain used for the Strimzi labels
      */

api/src/main/java/io/strimzi/api/kafka/Crds.java

@@ -59,8 +59,7 @@ public class Crds {
         KafkaNodePool.class
     };
 
-    private Crds() {
-    }
+    private Crds() { }
 
     @SuppressWarnings({"checkstyle:JavaNCSS"})
     private static CustomResourceDefinition crd(Class<? extends CustomResource> cls) {

api/src/main/java/io/strimzi/api/kafka/model/bridge/KafkaBridgeHttpConfig.java

@@ -38,8 +38,7 @@ public class KafkaBridgeHttpConfig implements UnknownPropertyPreserving {
     private KafkaBridgeHttpCors cors;
     private Map<String, Object> additionalProperties;
 
-    public KafkaBridgeHttpConfig() {
-    }
+    public KafkaBridgeHttpConfig() { }
 
     public KafkaBridgeHttpConfig(int port) {
         this.port = port;

api/src/main/java/io/strimzi/api/kafka/model/common/Constants.java

@@ -6,6 +6,8 @@
 package io.strimzi.api.kafka.model.common;
 
 public class Constants {
+    private Constants() { }
+
     public static final String RESOURCE_GROUP_NAME = "kafka.strimzi.io";
     public static final String RESOURCE_CORE_GROUP_NAME = "core.strimzi.io";
 

api/src/main/java/io/strimzi/api/kafka/model/common/CustomResourceConditions.java

@@ -30,8 +30,7 @@
  * </pre>
  */
 public class CustomResourceConditions {
-    private CustomResourceConditions() {
-    }
+    private CustomResourceConditions() { }
 
     /**
      * Returns a predicate that determines if CRD is ready. A CRD is

api/src/main/java/io/strimzi/api/kafka/model/common/Probe.java

@@ -35,8 +35,7 @@ public class Probe implements UnknownPropertyPreserving {
     private Integer failureThreshold;
     private Map<String, Object> additionalProperties;
 
-    public Probe() {
-    }
+    public Probe() { }
 
     public Probe(int initialDelaySeconds, int timeoutSeconds) {
         this.initialDelaySeconds = initialDelaySeconds;

api/src/main/java/io/strimzi/api/kafka/model/common/Rack.java

@@ -33,8 +33,7 @@ public class Rack implements UnknownPropertyPreserving {
     private String topologyKey;
     private Map<String, Object> additionalProperties;
 
-    public Rack() {
-    }
+    public Rack() { }
 
     public Rack(String topologyKey) {
         this.topologyKey = topologyKey;