List.contains in not working

Question

I have to get subset of users who do not have records in custom table last modified in last 15 minutes. Here is my code:

string query = 'Select Id FROM MyCustomObject__c where LastModifiedDate > ' + Datetime.now().addMinutes(15);

List<MyCustomObject__c> sobjList = Database.query(query);

List<String> userIdsToRemove = new List<String>();
for (MyCustomObject__c dataGrid :sobjList)
{
    userIdsToRemove.Add(dataGrid.Id);
}

List<User> allUsers = [select Id FROM User WHERE Profile.UserLicense.Name IN ('Salesforce','Salesforce Platform') AND 
                    IsActive=TRUE];
for (User u :allUsers)
{
    if (!userIdsToRemove.contains(u.Id))
    {
        usersToUpdate.Add(u);
    }
}

I get the following error: Error: Compile Error: Method does not exist or incorrect signature: [List].contains(Id) Why is my code complaining about contains()? Is there a way to optimize this code

Answer 1

The List class does not have a contains method. Use the Set class instead:

Set<Id> userIdsToRemove = new Set<Id>();
if (!userIdsToRemove.contains(u.Id)) { /* do stuff */ }

Answer 2

Since so many people have viewed this question, I wanted to provide an updated answer to this for anybody who visits this question in 2018 & beyond: The upcoming version of Salesforce (Spring '18) does add the contains() method to List: Spring '18 Release Notes: New and Changed Classes

contains(listElement)

Returns true if the list contains the specified element.

Answer 3

Contains is the Set Class method not the list class.. as the query return the list . You need to convert list to set and then You can use the contains method..You use other comparison operator with the list..

https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_list.htm

https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_methods_system_set.htm

Answer 4

You can do something like below in your code. This is just for reference.

List<String> city = new List<String>();
city.add('Nagpur');
city.add('Hyderabad');
city.add('Mumbai');
city.add('Indor');
city.add('Chennai');
city.add('Amravati');
city.sort();

Set<String> setCity = new Set<String>(city);
System.debug('Set City : '+setCity);
System.debug(setCity.contains('Amravati'));