Remove unnecessary generic type in Collections.empty*,

replace "for" on Stream API,
replace anonymous classes on lambda

processor/src/main/java/org/mapstruct/ap/MappingProcessor.java

@@ -341,10 +341,7 @@ public class MappingProcessor extends AbstractProcessor {
 
         @Override
         public int compare(ModelElementProcessor<?, ?> o1, ModelElementProcessor<?, ?> o2) {
-            return
+            return Integer.compare( o1.getPriority(), o2.getPriority() );
-                o1.getPriority() < o2.getPriority() ? -1 :
-                    o1.getPriority() == o2.getPriority() ? 0 :
-                        1;
         }
     }
 }

processor/src/main/java/org/mapstruct/ap/internal/conversion/DateToStringConversion.java

@@ -15,7 +15,6 @@ import org.mapstruct.ap.internal.model.HelperMethod;
 import org.mapstruct.ap.internal.model.TypeConversion;
 import org.mapstruct.ap.internal.model.common.Assignment;
 import org.mapstruct.ap.internal.model.common.ConversionContext;
-import org.mapstruct.ap.internal.model.common.Type;
 
 import static java.util.Arrays.asList;
 import static org.mapstruct.ap.internal.util.Collections.asSet;
@@ -31,7 +30,7 @@ public class DateToStringConversion implements ConversionProvider {
     @Override
     public Assignment to(ConversionContext conversionContext) {
         return new TypeConversion( asSet( conversionContext.getTypeFactory().getType( SimpleDateFormat.class ) ),
-            Collections.<Type>emptyList(),
+            Collections.emptyList(),
             getConversionExpression( conversionContext, "format" )
         );
     }

processor/src/main/java/org/mapstruct/ap/internal/model/Annotation.java

@@ -27,7 +27,7 @@ public class Annotation extends ModelElement {
     private List<String> properties;
 
     public Annotation(Type type) {
-        this( type, Collections.<String>emptyList() );
+        this( type, Collections.emptyList() );
     }
 
     public Annotation(Type type, List<String> properties) {

processor/src/main/java/org/mapstruct/ap/internal/model/BeanMappingMethod.java

@@ -17,9 +17,11 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.Objects;
 import java.util.Set;
 import java.util.function.Consumer;
 import java.util.function.Function;
+import java.util.stream.Collectors;
 import javax.lang.model.type.DeclaredType;
 import javax.tools.Diagnostic;
 
@@ -104,7 +106,7 @@ public class BeanMappingMethod extends NormalTypeMappingMethod {
             singleMapping =
                 targetName -> getMappingByTargetName( targetName, sourceMethod.getMappingOptions().getMappings() );
             mappingsInitializer =
-                mappings -> mappings.stream().forEach( mapping -> initReferencesForSourceMethodMapping( mapping ) );
+                mappings -> mappings.stream().forEach( this::initReferencesForSourceMethodMapping );
             this.method = sourceMethod;
             return this;
         }
@@ -112,7 +114,7 @@ public class BeanMappingMethod extends NormalTypeMappingMethod {
         public Builder forgedMethod(Method method) {
             singleMapping = targetPropertyName -> null;
             mappingsInitializer =
-                mappings -> mappings.stream().forEach( mapping -> initReferencesForForgedMethodMapping( mapping ) );
+                mappings -> mappings.stream().forEach( this::initReferencesForForgedMethodMapping );
             this.method = method;
             return this;
         }
@@ -177,8 +179,9 @@ public class BeanMappingMethod extends NormalTypeMappingMethod {
                     continue;
                 }
                 Map<String, Accessor> readAccessors = sourceParameter.getType().getPropertyReadAccessors();
-                for ( String key : readAccessors.keySet() ) {
+
-                    unprocessedSourceProperties.put( key, readAccessors.get( key ) );
+                for ( Entry<String, Accessor> entry : readAccessors.entrySet() ) {
+                    unprocessedSourceProperties.put( entry.getKey(), entry.getValue() );
                 }
             }
             existingVariableNames.addAll( method.getParameterNames() );
@@ -191,8 +194,8 @@ public class BeanMappingMethod extends NormalTypeMappingMethod {
             }
 
             // map properties with mapping
-            boolean mappingErrorOccured = handleDefinedMappings();
+            boolean mappingErrorOccurred = handleDefinedMappings();
-            if ( mappingErrorOccured ) {
+            if ( mappingErrorOccurred ) {
                 return null;
             }
 
@@ -366,13 +369,9 @@ public class BeanMappingMethod extends NormalTypeMappingMethod {
             }
             else {
                 Collections.sort(
-                    propertyMappings, new Comparator<PropertyMapping>() {
+                    propertyMappings,
-                        @Override
+                    Comparator.comparingInt( propertyMapping ->
-                        public int compare(PropertyMapping o1, PropertyMapping o2) {
+                            graphAnalyzer.getTraversalSequence( propertyMapping.getName() ) )
-                            return graphAnalyzer.getTraversalSequence( o1.getName() )
-                                - graphAnalyzer.getTraversalSequence( o2.getName() );
-                        }
-                    }
                 );
             }
         }
@@ -512,9 +511,8 @@ public class BeanMappingMethod extends NormalTypeMappingMethod {
          */
         private static boolean isValidWhenReversed(Mapping mapping) {
             if ( mapping.getInheritContext() != null && mapping.getInheritContext().isReversed() ) {
-                return mapping.getTargetReference().isValid() && ( mapping.getSourceReference() != null ?
+                return mapping.getTargetReference().isValid() && ( mapping.getSourceReference() == null ||
-                    mapping.getSourceReference().isValid() :
+                    mapping.getSourceReference().isValid() );
-                    true );
             }
             return true;
         }
@@ -1051,24 +1049,15 @@ public class BeanMappingMethod extends NormalTypeMappingMethod {
     }
 
     public List<Parameter> getSourceParametersExcludingPrimitives() {
-        List<Parameter> sourceParameters = new ArrayList<>();
+        return getSourceParameters().stream()
-        for ( Parameter sourceParam : getSourceParameters() ) {
+                            .filter( parameter -> !parameter.getType().isPrimitive() )
-            if ( !sourceParam.getType().isPrimitive() ) {
+                            .collect( Collectors.toList() );
-                sourceParameters.add( sourceParam );
-            }
-        }
-
-        return sourceParameters;
     }
 
     public List<Parameter> getSourcePrimitiveParameters() {
-        List<Parameter> sourceParameters = new ArrayList<>();
+        return getSourceParameters().stream()
-        for ( Parameter sourceParam : getSourceParameters() ) {
+                            .filter( parameter -> parameter.getType().isPrimitive() )
-            if ( sourceParam.getType().isPrimitive() ) {
+                            .collect( Collectors.toList() );
-                sourceParameters.add( sourceParam );
-            }
-        }
-        return sourceParameters;
     }
 
     @Override
@@ -1092,8 +1081,7 @@ public class BeanMappingMethod extends NormalTypeMappingMethod {
         if ( !super.equals( obj ) ) {
             return false;
         }
-        return propertyMappings != null ? propertyMappings.equals( that.propertyMappings ) :
+        return Objects.equals( propertyMappings, that.propertyMappings );
-            that.propertyMappings == null;
     }
 
     private interface SingleMappingByTargetPropertyNameFunction {

processor/src/main/java/org/mapstruct/ap/internal/model/LifecycleMethodResolver.java

@@ -9,6 +9,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 import org.mapstruct.ap.internal.model.common.Parameter;
 import org.mapstruct.ap.internal.model.common.Type;
@@ -123,9 +124,7 @@ public final class LifecycleMethodResolver {
         List<SourceMethod> availableMethods =
             new ArrayList<>( methodsProvidedByParams.size() + sourceModelMethods.size() );
 
-        for ( SourceMethod methodProvidedByParams : methodsProvidedByParams ) {
+        availableMethods.addAll( methodsProvidedByParams );
-            availableMethods.add( methodProvidedByParams );
-        }
         availableMethods.addAll( sourceModelMethods );
 
         return availableMethods;
@@ -141,7 +140,7 @@ public final class LifecycleMethodResolver {
         List<SelectedMethod<SourceMethod>> matchingMethods = selectors.getMatchingMethods(
             method,
             callbackMethods,
-            Collections.<Type> emptyList(),
+            Collections.emptyList(),
             targetType,
             SelectionCriteria.forLifecycleMethods( selectionParameters ) );
 
@@ -185,24 +184,14 @@ public final class LifecycleMethodResolver {
     }
 
     private static List<SourceMethod> filterBeforeMappingMethods(List<SourceMethod> methods) {
-        List<SourceMethod> result = new ArrayList<>();
+        return methods.stream()
-        for ( SourceMethod method : methods ) {
+                      .filter( SourceMethod::isBeforeMappingMethod )
-            if ( method.isBeforeMappingMethod() ) {
+                      .collect( Collectors.toList() );
-                result.add( method );
-            }
-        }
-
-        return result;
     }
 
     private static List<SourceMethod> filterAfterMappingMethods(List<SourceMethod> methods) {
-        List<SourceMethod> result = new ArrayList<>();
+        return methods.stream()
-        for ( SourceMethod method : methods ) {
+                      .filter( SourceMethod::isAfterMappingMethod )
-            if ( method.isAfterMappingMethod() ) {
+                      .collect( Collectors.toList() );
-                result.add( method );
-            }
-        }
-
-        return result;
     }
 }

processor/src/main/java/org/mapstruct/ap/internal/model/MethodReference.java

@@ -235,8 +235,7 @@ public class MethodReference extends ModelElement implements Assignment {
 
     @Override
     public List<Type> getThrownTypes() {
-        List<Type> exceptions = new ArrayList<>();
+        List<Type> exceptions = new ArrayList<>( thrownTypes );
-        exceptions.addAll( thrownTypes );
         if ( assignment != null ) {
             exceptions.addAll( assignment.getThrownTypes() );
         }

processor/src/main/java/org/mapstruct/ap/internal/model/common/TypeFactory.java

@@ -68,12 +68,7 @@ import static org.mapstruct.ap.internal.model.common.ImplementationType.withLoad
 public class TypeFactory {
 
     private static final Extractor<BuilderInfo, String> BUILDER_INFO_CREATION_METHOD_EXTRACTOR =
-        new Extractor<BuilderInfo, String>() {
+        builderInfo -> builderInfo.getBuilderCreationMethod().toString();
-            @Override
-            public String apply(BuilderInfo builderInfo) {
-                return builderInfo.getBuilderCreationMethod().toString();
-            }
-        };
 
     private final Elements elementUtils;
     private final Types typeUtils;

processor/src/main/java/org/mapstruct/ap/internal/model/source/MappingOptions.java

@@ -85,7 +85,7 @@ public class MappingOptions {
             null,
             null,
             forForgedMethods ? BeanMapping.forForgedMethods() : null,
-            Collections.<ValueMapping>emptyList(),
+            Collections.emptyList(),
             restrictToDefinedMappings
         );
 

processor/src/main/java/org/mapstruct/ap/internal/model/source/SelectionParameters.java

@@ -144,8 +144,8 @@ public class SelectionParameters {
 
     public static SelectionParameters forSourceRHS(SourceRHS sourceRHS) {
         return new SelectionParameters(
-            Collections.<TypeMirror>emptyList(),
+            Collections.emptyList(),
-            Collections.<String>emptyList(),
+            Collections.emptyList(),
             null,
             null,
             sourceRHS

processor/src/main/java/org/mapstruct/ap/internal/model/source/SourceReference.java

@@ -20,7 +20,6 @@ import javax.lang.model.type.DeclaredType;
 import org.mapstruct.ap.internal.model.common.Parameter;
 import org.mapstruct.ap.internal.model.common.Type;
 import org.mapstruct.ap.internal.model.common.TypeFactory;
-import org.mapstruct.ap.internal.util.Extractor;
 import org.mapstruct.ap.internal.util.FormattingMessager;
 import org.mapstruct.ap.internal.util.Message;
 import org.mapstruct.ap.internal.util.Strings;
@@ -214,12 +213,7 @@ public class SourceReference {
                         Strings.join(
                             method.getSourceParameters(),
                             ", ",
-                            new Extractor<Parameter, String>() {
+                            Parameter::getName
-                                @Override
-                                public String apply(Parameter parameter) {
-                                    return parameter.getName();
-                                }
-                            }
                         )
                     );
                 }

processor/src/main/java/org/mapstruct/ap/internal/util/AnnotationProcessorContext.java

@@ -6,7 +6,6 @@
 package org.mapstruct.ap.internal.util;
 
 import java.util.ArrayList;
-import java.util.Iterator;
 import java.util.List;
 import java.util.ServiceLoader;
 
@@ -113,8 +112,8 @@ public class AnnotationProcessorContext implements MapStructProcessingEnvironmen
                 AstModifyingAnnotationProcessor.class, AnnotationProcessorContext.class.getClassLoader()
         );
 
-        for ( Iterator<AstModifyingAnnotationProcessor> it = loader.iterator(); it.hasNext(); ) {
+        for ( AstModifyingAnnotationProcessor astModifyingAnnotationProcessor : loader ) {
-            processors.add( it.next() );
+            processors.add( astModifyingAnnotationProcessor );
         }
 
         return processors;

processor/src/main/java/org/mapstruct/ap/internal/util/Fields.java

@@ -84,9 +84,7 @@ public class Fields {
 
     private static void addFields(List<VariableElement> alreadyCollected, List<VariableElement> variablesToAdd) {
         List<VariableElement> safeToAdd = new ArrayList<>( variablesToAdd.size() );
-        for ( VariableElement toAdd : variablesToAdd ) {
+        safeToAdd.addAll( variablesToAdd );
-            safeToAdd.add( toAdd );
-        }
 
         alreadyCollected.addAll( 0, safeToAdd );
     }

processor/src/main/java/org/mapstruct/ap/internal/util/MapperConfiguration.java

@@ -99,8 +99,7 @@ public class MapperConfiguration {
     }
 
     public List<TypeMirror> imports() {
-        List<TypeMirror> imports = new ArrayList<>();
+        List<TypeMirror> imports = new ArrayList<>( mapperPrism.imports() );
-        imports.addAll( mapperPrism.imports() );
         if ( mapperConfigPrism != null ) {
             imports.addAll( mapperConfigPrism.imports() );
         }
@@ -262,7 +261,7 @@ public class MapperConfiguration {
 
     public boolean isDisableSubMappingMethodsGeneration() {
         if ( mapperPrism.disableSubMappingMethodsGeneration() ) {
-            return mapperPrism.disableSubMappingMethodsGeneration();
+            return true;
         }
 
         if ( mapperConfigPrism != null && mapperConfigPrism.disableSubMappingMethodsGeneration() ) {