diff --git a/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/ApexMetricsComputer.java b/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/ApexMetricsComputer.java
index 74ca07e3ff..d0d82c3d63 100644
--- a/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/ApexMetricsComputer.java
+++ b/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/ApexMetricsComputer.java
@@ -4,6 +4,7 @@
 
 package net.sourceforge.pmd.lang.apex.metrics;
 
+import java.util.ArrayList;
 import java.util.List;
 
 import net.sourceforge.pmd.lang.apex.ast.ASTMethod;
@@ -12,14 +13,23 @@ import net.sourceforge.pmd.lang.metrics.AbstractMetricsComputer;
 
 /**
  * Computes metrics for the Apex framework.
+ *
  * @author Clément Fournier
  */
 public class ApexMetricsComputer extends AbstractMetricsComputer<ASTUserClassOrInterface<?>, ASTMethod> {
 
-    public static final ApexMetricsComputer INSTANCE = new ApexMetricsComputer();
+    static final ApexMetricsComputer INSTANCE = new ApexMetricsComputer();
+
 
     @Override
     protected List<ASTMethod> findOperations(ASTUserClassOrInterface<?> node) {
-        return node.findChildrenOfType(ASTMethod.class);
+        List<ASTMethod> candidates = node.findChildrenOfType(ASTMethod.class);
+        List<ASTMethod> result = new ArrayList<>(candidates);
+        for (ASTMethod method : candidates) {
+            if (method.getImage().matches("(<clinit>|<init>|clone)")) {
+                result.remove(method);
+            }
+        }
+        return result;
     }
 }
diff --git a/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/AbstractApexClassMetric.java b/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/AbstractApexClassMetric.java
index 876a65585a..02d6588a5e 100644
--- a/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/AbstractApexClassMetric.java
+++ b/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/AbstractApexClassMetric.java
@@ -10,6 +10,8 @@ import net.sourceforge.pmd.lang.apex.metrics.AbstractApexMetric;
 import net.sourceforge.pmd.lang.apex.metrics.api.ApexClassMetric;
 
 /**
+ * Base class for Apex metrics.
+ *
  * @author Clément Fournier
  */
 public abstract class AbstractApexClassMetric extends AbstractApexMetric implements ApexClassMetric {
diff --git a/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/AbstractApexOperationMetric.java b/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/AbstractApexOperationMetric.java
index cdbc31b46c..ad8a1e54d2 100644
--- a/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/AbstractApexOperationMetric.java
+++ b/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/AbstractApexOperationMetric.java
@@ -10,10 +10,20 @@ import net.sourceforge.pmd.lang.apex.metrics.AbstractApexMetric;
 import net.sourceforge.pmd.lang.apex.metrics.api.ApexOperationMetric;
 
 /**
+ * Base class for Apex operation metrics.
+ *
  * @author Clément Fournier
  */
 public abstract class AbstractApexOperationMetric extends AbstractApexMetric implements ApexOperationMetric {
 
+    /**
+     * Checks if the metric can be computed on the node. For now, we filter out {@literal <clinit>, <init> and clone},
+     * which are present in all apex class nodes even if they're not implemented, which may yield unexpected results.
+     *
+     * @param node The node to check
+     *
+     * @return True if the metric can be computed
+     */
     @Override
     public boolean supports(ASTMethod node) {
         return !node.getImage().matches("(<clinit>|<init>|clone)")
diff --git a/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/CycloMetric.java b/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/CycloMetric.java
index 680680846b..737aad1b34 100644
--- a/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/CycloMetric.java
+++ b/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/CycloMetric.java
@@ -29,8 +29,16 @@ public class CycloMetric extends AbstractApexOperationMetric {
     public double computeFor(ASTMethod node, MetricVersion version) {
         return ((MutableInt) node.jjtAccept(new StandardCycloVisitor(), new MutableInt(1))).doubleValue();
     }
+    
 
-
+    /**
+     * Computes the number of control flow paths through that expression, which is the number of {@code ||} and {@code
+     * &&} operators. Used both by Npath and Cyclo.
+     *
+     * @param expression Boolean expression
+     *
+     * @return The complexity of the expression
+     */
     public static int booleanExpressionComplexity(ASTStandardCondition expression) {
         Set<ASTBooleanExpression> subs = new HashSet<>(expression.findDescendantsOfType(ASTBooleanExpression.class));
         int complexity = 0;
diff --git a/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/WmcMetric.java b/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/WmcMetric.java
index 7f6b8c4333..136dad1d50 100644
--- a/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/WmcMetric.java
+++ b/pmd-apex/src/main/java/net/sourceforge/pmd/lang/apex/metrics/impl/WmcMetric.java
@@ -11,6 +11,8 @@ import net.sourceforge.pmd.lang.metrics.MetricVersion;
 import net.sourceforge.pmd.lang.metrics.ResultOption;
 
 /**
+ * See the doc for the Java metric.
+ *
  * @author Clément Fournier
  */
 public class WmcMetric extends AbstractApexClassMetric {
diff --git a/pmd-apex/src/test/java/net/sourceforge/pmd/lang/apex/metrics/ApexProjectMirrorTest.java b/pmd-apex/src/test/java/net/sourceforge/pmd/lang/apex/metrics/ApexProjectMirrorTest.java
index 2ba6875626..6a12068c48 100644
--- a/pmd-apex/src/test/java/net/sourceforge/pmd/lang/apex/metrics/ApexProjectMirrorTest.java
+++ b/pmd-apex/src/test/java/net/sourceforge/pmd/lang/apex/metrics/ApexProjectMirrorTest.java
@@ -14,7 +14,6 @@ import java.util.Random;
 
 import org.junit.Test;
 
-import net.sourceforge.pmd.lang.MetricKeyUtil;
 import net.sourceforge.pmd.lang.apex.ast.ASTMethod;
 import net.sourceforge.pmd.lang.apex.ast.ASTUserClass;
 import net.sourceforge.pmd.lang.apex.ast.ASTUserClassOrInterface;
@@ -24,6 +23,7 @@ import net.sourceforge.pmd.lang.apex.metrics.impl.AbstractApexClassMetric;
 import net.sourceforge.pmd.lang.apex.metrics.impl.AbstractApexOperationMetric;
 import net.sourceforge.pmd.lang.metrics.Metric.Version;
 import net.sourceforge.pmd.lang.metrics.MetricKey;
+import net.sourceforge.pmd.lang.metrics.MetricKeyUtil;
 import net.sourceforge.pmd.lang.metrics.MetricMemoizer;
 import net.sourceforge.pmd.lang.metrics.MetricVersion;
 
diff --git a/pmd-core/src/main/java/net/sourceforge/pmd/lang/MetricKeyUtil.java b/pmd-core/src/main/java/net/sourceforge/pmd/lang/metrics/MetricKeyUtil.java
similarity index 92%
rename from pmd-core/src/main/java/net/sourceforge/pmd/lang/MetricKeyUtil.java
rename to pmd-core/src/main/java/net/sourceforge/pmd/lang/metrics/MetricKeyUtil.java
index 79a2ed8971..6ede93208a 100644
--- a/pmd-core/src/main/java/net/sourceforge/pmd/lang/MetricKeyUtil.java
+++ b/pmd-core/src/main/java/net/sourceforge/pmd/lang/metrics/MetricKeyUtil.java
@@ -2,13 +2,11 @@
  * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
  */
 
-package net.sourceforge.pmd.lang;
+package net.sourceforge.pmd.lang.metrics;
 
 import java.util.Objects;
 
 import net.sourceforge.pmd.lang.ast.Node;
-import net.sourceforge.pmd.lang.metrics.Metric;
-import net.sourceforge.pmd.lang.metrics.MetricKey;
 
 /**
  * Holds the key creation method until we move it to the MetricKey interface.
diff --git a/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/ParameterizedMetricKeyTest.java b/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/ParameterizedMetricKeyTest.java
index e433861d14..23a8ab7f03 100644
--- a/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/ParameterizedMetricKeyTest.java
+++ b/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/ParameterizedMetricKeyTest.java
@@ -12,11 +12,11 @@ import static org.junit.Assert.assertTrue;
 
 import org.junit.Test;
 
-import net.sourceforge.pmd.lang.MetricKeyUtil;
 import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeDeclaration;
 import net.sourceforge.pmd.lang.java.metrics.api.JavaClassMetricKey;
 import net.sourceforge.pmd.lang.java.metrics.api.JavaOperationMetricKey;
 import net.sourceforge.pmd.lang.metrics.MetricKey;
+import net.sourceforge.pmd.lang.metrics.MetricKeyUtil;
 import net.sourceforge.pmd.lang.metrics.MetricVersion;
 import net.sourceforge.pmd.lang.metrics.ParameterizedMetricKey;
 
diff --git a/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/ProjectMemoizerTest.java b/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/ProjectMemoizerTest.java
index f5ea7c30eb..35e8f320ba 100644
--- a/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/ProjectMemoizerTest.java
+++ b/pmd-java/src/test/java/net/sourceforge/pmd/lang/java/metrics/ProjectMemoizerTest.java
@@ -14,7 +14,6 @@ import java.util.Random;
 
 import org.junit.Test;
 
-import net.sourceforge.pmd.lang.MetricKeyUtil;
 import net.sourceforge.pmd.lang.java.ast.ASTAnyTypeDeclaration;
 import net.sourceforge.pmd.lang.java.ast.ASTCompilationUnit;
 import net.sourceforge.pmd.lang.java.ast.ASTMethodOrConstructorDeclaration;
@@ -24,6 +23,7 @@ import net.sourceforge.pmd.lang.java.metrics.impl.AbstractJavaOperationMetric;
 import net.sourceforge.pmd.lang.java.metrics.testdata.MetricsVisitorTestData;
 import net.sourceforge.pmd.lang.metrics.Metric.Version;
 import net.sourceforge.pmd.lang.metrics.MetricKey;
+import net.sourceforge.pmd.lang.metrics.MetricKeyUtil;
 import net.sourceforge.pmd.lang.metrics.MetricMemoizer;
 import net.sourceforge.pmd.lang.metrics.MetricVersion;
 
diff --git a/src/site/markdown/overview/changelog.md b/src/site/markdown/overview/changelog.md
index 2c02b85ceb..26d98f53d7 100644
--- a/src/site/markdown/overview/changelog.md
+++ b/src/site/markdown/overview/changelog.md
@@ -132,4 +132,5 @@ and include them to such reports.
 *   [#530](https://github.com/pmd/pmd/pull/530): \[java] Fix issue #527: Lombok getter annotation on enum is not recognized correctly - [Clément Fournier](https://github.com/oowekyala)
 *   [#535](https://github.com/pmd/pmd/pull/535): \[apex] Fix broken Apex visitor adapter - [Clément Fournier](https://github.com/oowekyala)
 *   [#529](https://github.com/pmd/pmd/pull/529): \[java] Abstracted the Java metrics framework - [Clément Fournier](https://github.com/oowekyala)
+*   [#542](https://github.com/pmd/pmd/pull/542): \[java] Metrics abstraction - [Clément Fournier](https://github.com/oowekyala)