reta commented on a change in pull request #407: [CXF-7716] Reduce 
StringBuilders and other performance changes.
URL: https://github.com/apache/cxf/pull/407#discussion_r183578479
 
 

 ##########
 File path: 
rt/frontend/jaxrs/src/main/java/org/apache/cxf/jaxrs/utils/JAXRSUtils.java
 ##########
 @@ -1508,11 +1509,40 @@ public static boolean matchMimeTypes(MediaType 
requestContentType,
                 }
             }
         }
-
         return new ArrayList<>(supportedMimeTypeList);
+    }
+
+    public static boolean doMimeTypesIntersect(List<MediaType> 
requiredMediaTypes, List<MediaType> userMediaTypes) {
+        for (MediaType requiredType : requiredMediaTypes) {
 
 Review comment:
   Turned out to be quite tricky ... but I have one suggestion for you. Here is 
the implementation for `doMimeTypesIntersect` and `intersectMimeTypes`:
   
   ```
     public static List<MediaType> intersectMimeTypes(List<MediaType> 
requiredMediaTypes,
                                                        List<MediaType> 
userMediaTypes,
                                                        boolean 
addRequiredParamsIfPossible,
                                                        boolean 
addDistanceParameter) {
           final AccumulatingConsumer consumer = new 
AccumulatingConsumer(addRequiredParamsIfPossible, addDistanceParameter);
           intersectMimeTypes(requiredMediaTypes, userMediaTypes, consumer);
           return new ArrayList<>(consumer.supportedMimeTypeList);
       }
       
       public static boolean doMimeTypesIntersect(List<MediaType> 
requiredMediaTypes, List<MediaType> userMediaTypes) {
           final NonAccumulatingConsumer consumer = new 
NonAccumulatingConsumer();
           intersectMimeTypes(requiredMediaTypes, userMediaTypes, consumer);
           return consumer.doIntersect;
       }
   ```
   Here is the initial `intersectMimeTypes` function, refactored to use 
consumers, the part which is was accumulating (or returning `true`) is now part 
of the consumers:
   
   ```
   private static void intersectMimeTypes(List<MediaType> requiredMediaTypes, 
List<MediaType> userMediaTypes,
               BiConsumer<MediaType, MediaType> consumer) {
   
           for (MediaType requiredType : requiredMediaTypes) {
               for (MediaType userType : userMediaTypes) {
                   boolean isCompatible = isMediaTypeCompatible(requiredType, 
userType);
                   if (isCompatible) {
                       boolean parametersMatched = true;
                       for (Map.Entry<String, String> entry : 
userType.getParameters().entrySet()) {
                           String value = 
requiredType.getParameters().get(entry.getKey());
                           if (value != null && entry.getValue() != null
                               && !(stripDoubleQuotesIfNeeded(value).equals(
                                       
stripDoubleQuotesIfNeeded(entry.getValue())))) {
                               
                               if (HTTP_CHARSET_PARAM.equals(entry.getKey())
                                   && value.equalsIgnoreCase(entry.getValue())) 
{
                                   continue;
                               }
                               parametersMatched = false;
                               break;
                           }
                       }
                       if (!parametersMatched) {
                           continue;
                       }
                       
                       consumer.accept(requiredType, userType);
                   }
               }
           }
       }
   
   ```
   
   And finally, two consumers:
   ```
       private static class NonAccumulatingConsumer implements 
BiConsumer<MediaType, MediaType> {
           private boolean doIntersect;
           
           @Override
           public void accept(MediaType t, MediaType u) {
               doIntersect = true;
           }
       }
   ```
   
   And 
   ```
       private static class AccumulatingConsumer implements 
BiConsumer<MediaType, MediaType> {
           private final Set<MediaType> supportedMimeTypeList = new 
LinkedHashSet<MediaType>();
           private final boolean addRequiredParamsIfPossible;
           private final boolean addDistanceParameter;
           
           private AccumulatingConsumer(boolean addRequiredParamsIfPossible, 
boolean addDistanceParameter) {
               this.addRequiredParamsIfPossible = addRequiredParamsIfPossible;
               this.addDistanceParameter = addDistanceParameter;
           }
           
           @Override
           public void accept(MediaType requiredType, MediaType userType) {
               boolean requiredTypeWildcard = 
requiredType.getType().equals(MediaType.MEDIA_TYPE_WILDCARD);
               boolean requiredSubTypeWildcard = 
requiredType.getSubtype().contains(MediaType.MEDIA_TYPE_WILDCARD);
   
               String type = requiredTypeWildcard ? userType.getType() : 
requiredType.getType();
               String subtype = requiredSubTypeWildcard ? userType.getSubtype() 
: requiredType.getSubtype();
   
               Map<String, String> parameters = userType.getParameters();
               if (addRequiredParamsIfPossible) {
                   parameters = new LinkedHashMap<String, String>(parameters);
                   for (Map.Entry<String, String> entry : 
requiredType.getParameters().entrySet()) {
                       if (!parameters.containsKey(entry.getKey())) {
                           parameters.put(entry.getKey(), entry.getValue());
                       }
                   }
               }
               if (addDistanceParameter) {
                   int distance = 0;
                   if (requiredTypeWildcard) {
                       distance++;
                   }
                   if (requiredSubTypeWildcard) {
                       distance++;
                   }
                   parameters.put(MEDIA_TYPE_DISTANCE_PARAM, 
Integer.toString(distance));
               }
               supportedMimeTypeList.add(new MediaType(type, subtype, 
parameters));
           }
       }
   ```
   
   Ideally, would be good to move to a dedicated utility class, but roughly 
this is an idea. What do you think. @WhiteCat22, does it make sense?

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