Merge branch 'pr-580'

docs/pages/release_notes.md

@@ -242,4 +242,5 @@ All existing rules have been updated to reflect these changes. If you have custo
 *   [#573](https://github.com/pmd/pmd/pull/573): \[java] Data class rule - [Clément Fournier](https://github.com/oowekyala)
 *   [#576](https://github.com/pmd/pmd/pull/576): \[doc]\[java] Add hint for Guava users in InefficientEmptyStringCheck - [mmoehring](https://github.com/mmoehring)
 *   [#578](https://github.com/pmd/pmd/pull/578): \[java] Refactored god class rule - [Clément Fournier](https://github.com/oowekyala)
+*   [#580](https://github.com/pmd/pmd/pull/580): \[core] Add AbstractMetric to topple the class hierarchy of metrics - [Clément Fournier](https://github.com/oowekyala)
 *   [#581](https://github.com/pmd/pmd/pull/581): \[java] Relax AbstractClassWithoutAnyMethod when class is annotated by @AutoValue - [Niklas Baudy](https://github.com/vanniktech)

pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/AbstractApexMetric.java

@@ -4,12 +4,16 @@
 
 package net.sourceforge.pmd.lang.apex.metrics;
 
+import net.sourceforge.pmd.lang.ast.Node;
+import net.sourceforge.pmd.lang.metrics.AbstractMetric;
+
 /**
  * Base class for all Apex metrics.
  *
  * @author Clément Fournier
  */
-public class AbstractApexMetric {
+public abstract class AbstractApexMetric<N extends Node> extends AbstractMetric<N> {
+
 
     protected ApexSignatureMatcher getSignatureMatcher() {
         return ApexMetrics.getFacade().getProjectMirror();

pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/AbstractApexClassMetric.java

@@ -14,7 +14,8 @@ import net.sourceforge.pmd.lang.apex.metrics.api.ApexClassMetric;
  *
  * @author Clément Fournier
  */
-public abstract class AbstractApexClassMetric extends AbstractApexMetric implements ApexClassMetric {
+public abstract class AbstractApexClassMetric extends AbstractApexMetric<ASTUserClassOrInterface<?>>
+    implements ApexClassMetric {
 
     @Override
     public boolean supports(ASTUserClassOrInterface<?> node) {

pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/AbstractApexOperationMetric.java

@@ -14,7 +14,7 @@ import net.sourceforge.pmd.lang.apex.metrics.api.ApexOperationMetric;
  *
  * @author Clément Fournier
  */
-public abstract class AbstractApexOperationMetric extends AbstractApexMetric implements ApexOperationMetric {
+public abstract class AbstractApexOperationMetric extends AbstractApexMetric<ASTMethod> implements ApexOperationMetric {
 
     /**
      * Checks if the metric can be computed on the node. For now, we filter out {@literal <clinit>, <init> and clone},

pmd-core/src/main/java/net/sourceforge/pmd/lang/metrics/AbstractMetric.java

@@ -0,0 +1,35 @@
+/**
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
+package net.sourceforge.pmd.lang.metrics;
+
+import net.sourceforge.pmd.lang.ast.Node;
+
+/**
+ * Abstract class for all metrics.
+ *
+ * @param <N> Type of nodes the metric can be computed on
+ *
+ * @author Clément Fournier
+ * @since 6.0.0
+ */
+public abstract class AbstractMetric<N extends Node> implements Metric<N> {
+
+    /**
+     * Metrics should be stateless, thus any instance of the same metric class should be equal.
+     *
+     * {@inheritDoc}
+     */
+    @Override
+    public final boolean equals(Object o) {
+        return o != null && o.getClass() == this.getClass();
+    }
+
+
+    @Override
+    public final int hashCode() {
+        return getClass().hashCode();
+    }
+
+}

pmd-java/src/main/java/net/sourceforge/pmd/lang/java/metrics/AbstractJavaMetric.java

@@ -10,7 +10,7 @@ import java.util.List;
 import net.sourceforge.pmd.lang.ast.Node;
 import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
 import net.sourceforge.pmd.lang.java.ast.JavaQualifiedName;
-import net.sourceforge.pmd.lang.metrics.Metric;
+import net.sourceforge.pmd.lang.metrics.AbstractMetric;
 
 
 /**
@@ -21,7 +21,7 @@ import net.sourceforge.pmd.lang.metrics.Metric;
  *
  * @author Clément Fournier
  */
-public abstract class AbstractJavaMetric<N extends Node> implements Metric<N> {
+public abstract class AbstractJavaMetric<N extends Node> extends AbstractMetric<N> {
 
 
     protected List<JavaQualifiedName> findAllCalls(ASTMethodOrConstructorDeclaration node) {
@@ -33,18 +33,6 @@ public abstract class AbstractJavaMetric<N extends Node> implements Metric<N> {
     }
 
 
-    @Override
-    public final boolean equals(Object o) {
-        return o != null && o.getClass() == this.getClass();
-    }
-
-
-    @Override
-    public final int hashCode() {
-        return getClass().hashCode();
-    }
-
-
     /**
      * Gives access to a signature matcher to metrics. They can use it to perform signature matching.
      *