Compare map value and set<string> and retain string that doesn't exist in set

Question

I'm iterating over below map. I want to compare map values and set and iterate over the map.values that doesn't exist in set

Set<String> articleIds = new Set<String>(); 

List<object__c> cuList = [SELECT Article_ID__c FROM object__c WHERE Article_ID__c IN: cuWrapperMap.keySet()];

            if((cuWrapperMap.keySet().size() > cuList.size()) && cuList.size() > 0){
                for(object__c cua : caList){
                    articleIds.add(cua.Article_ID__c);
                    for(articleWrapper wrpr : cuWrapperMap.values()){
                        //Here I want to iterate only for wrpr.articleId's that doesn't exist in the set.
                        if(!(wrpr.articleId).contains(articleIds)){

                            object__c cuaRec = new object__c();
                            cuaRec.Case__c = wrpr.caseId;
                            cuaRec.Article_ID__c = (wrpr.articleId).substring(0, 15);
                            createCUAList.add(cuaRec);
                        }
                    }    
                }

            }
insert createCUAList;

Answer 1

You are trying to use String class's contains method whereas you should be using Set class's contains method. And string's contains method does not take set as parameter, hence you might be receiving the compilation error.

String's contains method

contains(substring)

Returns true if and only if the String that called the method contains the specified sequence of characters in substring.

String myString1 = 'abcde';
String myString2 = 'abcd';
Boolean result = myString1.contains(myString2);
System.assertEquals(result, true);

Set's contains method

contains(setElement)

Returns true if the set contains the specified element.

Set<String> myString = new Set<String>{'a', 'b'};
Boolean result = myString.contains('z');
System.assertEquals(false, result);

So change your below code

if(!(wrpr.articleId).contains(articleIds))

to

if(!articleIds.contains(wrpr.articleId))

which will check if the wrpr.articleId is present in articleIds set or not