diff --git a/processor/src/main/java/org/mapstruct/ap/model/source/Method.java b/processor/src/main/java/org/mapstruct/ap/model/source/Method.java
index 473133022..7ad65143a 100644
--- a/processor/src/main/java/org/mapstruct/ap/model/source/Method.java
+++ b/processor/src/main/java/org/mapstruct/ap/model/source/Method.java
@@ -30,6 +30,7 @@ import org.mapstruct.ap.model.source.builtin.BuiltInMethod;
  * This interface makes available common method properties and a matching method
  *
  * There are 2 known implementors: {@link BuiltInMethod} and {@link Method}
+ *
  * @author Sjaak Derksen
  */
 public interface Method {
@@ -43,7 +44,7 @@ public interface Method {
      *
      * @return true when match
      */
-    boolean matches( Type sourceType, Type targetType );
+    boolean matches(Type sourceType, Type targetType);
 
     /**
      * Returns the mapper type declaring this method if it is not declared by the mapper interface currently processed
@@ -77,6 +78,7 @@ public interface Method {
 
     /**
      * Returns the parameter designated as target parameter (if present) {@link #getSourceParameters() }
+     *
      * @return target parameter (when present) null otherwise.
      */
     Parameter getTargetParameter();
diff --git a/processor/src/main/java/org/mapstruct/ap/model/source/MethodMatcher.java b/processor/src/main/java/org/mapstruct/ap/model/source/MethodMatcher.java
index 222396817..b488774ce 100644
--- a/processor/src/main/java/org/mapstruct/ap/model/source/MethodMatcher.java
+++ b/processor/src/main/java/org/mapstruct/ap/model/source/MethodMatcher.java
@@ -40,11 +40,11 @@ import org.mapstruct.ap.model.common.Type;
  * SourceMethodMatcher $8.4 of the JavaLanguage specification describes a method body as such:
  *
  * <pre>
- SourceMethodDeclaration: SourceMethodHeader SourceMethodBody
- SourceMethodHeader: SourceMethodModifiers TypeParameters Result SourceMethodDeclarator Throws
- SourceMethodDeclarator: Identifier ( FormalParameterList )
-
- example &lt;T extends String & Serializable&gt;  T   getResult(? extends T) throws Exception
+ * SourceMethodDeclaration: SourceMethodHeader SourceMethodBody
+ * SourceMethodHeader: SourceMethodModifiers TypeParameters Result SourceMethodDeclarator Throws
+ * SourceMethodDeclarator: Identifier ( FormalParameterList )
+ *
+ * example &lt;T extends String & Serializable&gt;  T   getResult(? extends T) throws Exception
  *         \-------------------------------/ \-/            \---------/
  *               TypeParameters             Result        ParameterList
  * </pre>
@@ -66,26 +66,21 @@ public class MethodMatcher {
     private final Types typeUtils;
     private final Map<TypeVariable, TypeMirror> genericTypesMap = new HashMap<TypeVariable, TypeMirror>();
 
-    /**
-     * package scope constructor
-     *
-     * @param typeUtils
-     * @param candidateMethod
-     */
     MethodMatcher(Types typeUtils, SourceMethod candidateMethod) {
         this.typeUtils = typeUtils;
         this.candidateMethod = candidateMethod;
     }
 
     /**
-     * package scoped method
+     * Whether the given source and target type are matched by this matcher's candidate method.
      *
-     * @param sourceType
-     * @param targetType
+     * @param sourceType the source type
+     * @param targetType the target type
      *
-     * @return true when both, sourceType and targetType matches the signature.
+     * @return {@code true} when both, source type and target type match the signature of this matcher's method;
+     *         {@code false} otherwise.
      */
-     boolean matches( Type sourceType, Type targetType ) {
+    boolean matches(Type sourceType, Type targetType) {
         // check & collect generic types.
         List<? extends VariableElement> candidateParameters = candidateMethod.getExecutable().getParameters();
 
diff --git a/processor/src/main/java/org/mapstruct/ap/model/source/builtin/BuiltInMethod.java b/processor/src/main/java/org/mapstruct/ap/model/source/builtin/BuiltInMethod.java
index 673fb8d10..95588492a 100644
--- a/processor/src/main/java/org/mapstruct/ap/model/source/builtin/BuiltInMethod.java
+++ b/processor/src/main/java/org/mapstruct/ap/model/source/builtin/BuiltInMethod.java
@@ -23,24 +23,22 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 
+import org.mapstruct.ap.conversion.SimpleConversion;
 import org.mapstruct.ap.model.common.Accessibility;
 import org.mapstruct.ap.model.common.ConversionContext;
-import org.mapstruct.ap.model.common.ModelElement;
 import org.mapstruct.ap.model.common.Parameter;
 import org.mapstruct.ap.model.common.Type;
 import org.mapstruct.ap.model.source.Method;
 import org.mapstruct.ap.util.Strings;
 
 /**
- * Implementations create:
- * 1) an implementation of this build in method.
- * 2) a reference to a build in method, to use in property mappings
- * 3) a name for logging purposes.
+ * Represents a "built-in" mapping method which will be added as private method to the generated mapper. Built-in
+ * methods are used in cases where a {@link SimpleConversion} doesn't suffice, e.g. as several lines of source code or a
+ * try/catch block are required.
  *
  * @author Sjaak Derksen
  */
-public abstract class BuiltInMethod extends ModelElement implements Method {
-
+public abstract class BuiltInMethod implements Method {
 
     /**
      * {@inheritDoc }
@@ -53,20 +51,19 @@ public abstract class BuiltInMethod extends ModelElement implements Method {
     }
 
     /**
-     * {@inheritDoc} {@link ModelElement}
+     * Returns the types used by this method for which import statements need to be generated. Defaults to the empty
+     * set. To be overridden by implementations in case they make use of additional types (note that the parameter and
+     * return type don't need to be added).
      *
-     * This method acts as a template. It should be overridden by implementors if deviation is required.
-     *
-     * @return set of used types. Default an empty set.
+     * @return the types used by this method for which import statements need to be generated
      */
-    @Override
     public Set<Type> getImportTypes() {
         return Collections.<Type>emptySet();
     }
 
     /**
-     * {@inheritDoc} {@link Method}
-     *
+     * {@inheritDoc}
+     * <p>
      * Default the targetType should be assignable to the returnType and the sourceType to the parameter,
      * excluding generic type variables. When the implementor sees a need for this, this method can be overridden.
      */
@@ -79,41 +76,33 @@ public abstract class BuiltInMethod extends ModelElement implements Method {
         return false;
     }
 
-    /**
-     * {@inheritDoc} {@link Method}
-     *
-     * @return all parameters are source parameters for build-in methods.
-     */
     @Override
     public List<Parameter> getSourceParameters() {
         return getParameters();
     }
 
     /**
-     * {@inheritDoc} {@link Method}
+     * {@inheritDoc}
+     * <p>
+     * For built-in methods, the declaring mapper is always {@code null} as they will be added as private methods to the
+     * generated mapper.
      *
-     * declaring mapper is always null, being the MapperImpl itself. This method should not be overridden by
-     * implementors
-     *
-     * @return null
+     * @return {@code null}
      */
     @Override
-    public Type getDeclaringMapper() {
+    public final Type getDeclaringMapper() {
         return null;
     }
 
-    /**
-     * {@inheritDoc} {@link Method}
-     */
     @Override
     public List<Parameter> getParameters() {
-        return Arrays.asList( new Parameter[] { getParameter() } );
+        return Arrays.asList( getParameter() );
     }
 
     /**
-     * target parameter mechanism not supported for build-in-method
+     * target parameter mechanism not supported for built-in methods
      *
-     * @return null
+     * @return {@code null}
      */
     @Override
     public Parameter getTargetParameter() {