Hi,


All I am trying to do is if the Opty status is changed to Stage A or Stage B  and if there are no Service contract associated with it then perform some action.

But my question is , Do I need to check  set size before calling contains() method on a set.
I have a trigger on opty where a set of Opty Ids are created,  if a Service contract is associated to it. But the set size (Set.size()>0) is not checked before using contains method (Set.sontains()). Even though its not throwing Dereference to null object , I want to understand what would a Contains method check if the set is empty and why is it not throwing any error.

Please advise.


Below is my code 
trigger trg_aftr_ins_upd on Opportunity (after insert, after update) {
    Boolean skipValidations = false;
    skipValidations = SkipTriggerValidation.performTriggerValidations();
    if(skipValidations == false){  
    Set<String> optyCancelledStages = new Set<String>();
        optyCancelledStages.add('Stage A');
        optyCancelledStages.add('Stage B');  
    Map<Id, String> optyIdProjectStatusMap = new Map<Id, String>();    
   
    Set<id> scOpptySet=new Set<id>();
    if(trigger.isupdate){
    for(ServiceContract sc:[select id,opportunity__c from ServiceContract where Opportunity__c in:trigger.newMap.keyset()]){
        scOpptySet.add(sc.opportunity__c);
        
    }
   }
   for(Opportunity o:Trigger.new)
   {
    Opportunity oldOpportunity = null;
        if(trigger.isUpdate){
        oldOpportunity = trigger.oldMap.get(o.Id);
        }   
          
           if(trigger.isUpdate && oldOpportunity.stageName != o.StageName  && optyCancelledStages.contains(o.StageName))
        {
          
            if( !scOpptySet.contains(o.id)  ) /// this is currently working but will this throw Derefernce to Null pointer in any scenario?                                                                              
                optyIdProjectStatusMap.put(o.Id, wfUtil.CANCELLED);
        }
          
      
        if(optyIdProjectStatusMap != null && !optyIdProjectStatusMap.isEmpty()){
            //Perform some action here......
        }
  }
 
 }