#vulnerable code 
                                private List<MappedProperty> getMappedProperties(ExecutableElement method, Map<String, Mapping> mappings) {
        Element returnTypeElement = typeUtils.asElement( method.getReturnType() );
        Element parameterElement = typeUtils.asElement( method.getParameters().get( 0 ).asType() );

        List<MappedProperty> properties = new ArrayList<MappedProperty>();
        List<ExecutableElement> sourceGetters = Filters.getterMethodsIn( parameterElement.getEnclosedElements() );
        List<ExecutableElement> targetSetters = Filters.setterMethodsIn( returnTypeElement.getEnclosedElements() );

        reportErrorIfMappedPropertiesDontExist( method, mappings, sourceGetters, targetSetters );

        for ( ExecutableElement getterMethod : sourceGetters ) {
            String sourcePropertyName = Executables.getPropertyName( getterMethod );
            Mapping mapping = mappings.get( sourcePropertyName );

            for ( ExecutableElement setterMethod : targetSetters ) {
                String targetPropertyName = Executables.getPropertyName( setterMethod );

                if ( targetPropertyName.equals( mapping != null ? mapping.getTargetName() : sourcePropertyName ) ) {
                    properties.add(
                        new MappedProperty(
                            sourcePropertyName,
                            getterMethod.getSimpleName().toString(),
                            Executables.getCorrespondingSetterMethod( parameterElement, getterMethod )
                                .getSimpleName()
                                .toString(),
                            retrieveReturnType( getterMethod ),
                            mapping != null ? mapping.getTargetName() : targetPropertyName,
                            Executables.getCorrespondingGetterMethod( returnTypeElement, setterMethod )
                                .getSimpleName()
                                .toString(),
                            setterMethod.getSimpleName().toString(),
                            retrieveParameter( setterMethod ).getType()
                        )
                    );
                }
            }
        }

        return properties;
    } 
                            #location 24 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                private List<MappedProperty> getMappedProperties(ExecutableElement method, Map<String, Mapping> mappings) {
        TypeElement returnTypeElement = (TypeElement) typeUtils.asElement( method.getReturnType() );
        TypeElement parameterElement = (TypeElement) typeUtils.asElement( method.getParameters().get( 0 ).asType() );

        List<MappedProperty> properties = new ArrayList<MappedProperty>();

        List<ExecutableElement> sourceGetters = Filters.getterMethodsIn(
            elementUtils.getAllMembers( parameterElement )
        );
        List<ExecutableElement> targetSetters = Filters.setterMethodsIn(
            elementUtils.getAllMembers( returnTypeElement )
        );
        List<ExecutableElement> sourceSetters = Filters.setterMethodsIn(
            elementUtils.getAllMembers( parameterElement )
        );
        List<ExecutableElement> targetGetters = Filters.getterMethodsIn(
            elementUtils.getAllMembers( returnTypeElement )
        );

        reportErrorIfMappedPropertiesDontExist( method, mappings, sourceGetters, targetSetters );

        for ( ExecutableElement getterMethod : sourceGetters ) {
            String sourcePropertyName = Executables.getPropertyName( getterMethod );
            Mapping mapping = mappings.get( sourcePropertyName );

            for ( ExecutableElement setterMethod : targetSetters ) {
                String targetPropertyName = Executables.getPropertyName( setterMethod );

                if ( targetPropertyName.equals( mapping != null ? mapping.getTargetName() : sourcePropertyName ) ) {
                    properties.add(
                        new MappedProperty(
                            sourcePropertyName,
                            getterMethod.getSimpleName().toString(),
                            Executables.getCorrespondingPropertyAccessor( getterMethod, sourceSetters )
                                .getSimpleName()
                                .toString(),
                            retrieveReturnType( getterMethod ),
                            mapping != null ? mapping.getTargetName() : targetPropertyName,
                            Executables.getCorrespondingPropertyAccessor( setterMethod, targetGetters )
                                .getSimpleName()
                                .toString(),
                            setterMethod.getSimpleName().toString(),
                            retrieveParameter( setterMethod ).getType()
                        )
                    );
                }
            }
        }

        return properties;
    }