Upgrade sonar to new 6.2 installation (#456)

* Upgrade to new sonar instance. Fix new identified issues.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

hawkbit-core/src/main/java/org/eclipse/hawkbit/artifact/repository/ArtifactStoreException.java

@@ -11,9 +11,6 @@ package org.eclipse.hawkbit.artifact.repository;
 /**
  * {@link ArtifactStoreException} is thrown in case storing of an artifact was
  * not successful.
- * 
- *
- *
  */
 public class ArtifactStoreException extends RuntimeException {
 
@@ -25,7 +22,7 @@ public class ArtifactStoreException extends RuntimeException {
      * @param message
      *            the message of the exception
      * @param cause
-     *            the cause of the exception
+     *            of the exception
      */
     public ArtifactStoreException(final String message, final Throwable cause) {
         super(message, cause);
@@ -40,4 +37,14 @@ public class ArtifactStoreException extends RuntimeException {
     public ArtifactStoreException(final String message) {
         super(message);
     }
+
+    /**
+     * Constructs a ArtifactStoreException with cause.
+     * 
+     * @param cause
+     *            of the exception
+     */
+    public ArtifactStoreException(final Throwable cause) {
+        super(cause);
+    }
 }

hawkbit-core/src/main/java/org/eclipse/hawkbit/cache/TenantAwareCacheManager.java

@@ -8,9 +8,8 @@
  */
 package org.eclipse.hawkbit.cache;
 
-import static java.util.Collections.emptyList;
-
 import java.util.Collection;
+import java.util.Collections;
 import java.util.stream.Collectors;
 
 import org.eclipse.hawkbit.tenancy.TenantAware;
@@ -64,7 +63,7 @@ public class TenantAwareCacheManager implements TenancyCacheManager {
     public Collection<String> getCacheNames() {
         String currentTenant = tenantAware.getCurrentTenant();
         if (isTenantInvalid(currentTenant)) {
-            return emptyList();
+            return Collections.emptyList();
         }
 
         currentTenant = currentTenant.toUpperCase();