trigger CreateOppLineItemNumber on OpportunityLineItem (after insert, before delete,after update) 
{
if(trigger.isInsert){
if(HandelRecurssiveTriggerOppLineItem.flag!=true){

createOppLineItemNumber.InsertingOppLineItems(trigger.new);
HandelRecurssiveTriggerOppLineItem.flag=true;
}
}
if(trigger.isUpdate ){
if(HandelRecurssiveTriggerOppLineItem.flag!=true){

createOppLineItemNumber.UpdatingOppLineItems(trigger.old);
HandelRecurssiveTriggerOppLineItem.flag=true;
}
}
if(trigger.isDelete){
createOppLineItemNumber.DeletingOppLineItems(trigger.old);
}
}

public class createOppLineItemNumber{

map<Id,Opportunity> mapopps = new map<Id,Opportunity>();

 public static void InsertingOppLineItems( OpportunityLineItem  [] OLits){
 List <OpportunityLineItem> UpdateOli = New List <OpportunityLineItem>();
 set<id> setopids = new set<id>();
for(OpportunityLineItem oli : OLits)
  {

   if(oli.opportunityId!=null)
   Setopids.add(oli.opportunityId);
 }
  map<Id, Opportunity> mapOpp= new map<Id, Opportunity>([SELECT Id,DeletedOpplineHold__c,totlanonnullcounts__c from Opportunity Where Id IN :setopids ]);

   integer i=0;

  for(OpportunityLineItem oplin :OLits)
  {

   integer res=integer.valueof((mapopp.get(oplin.opportunityId).totlanonnullcounts__c!=null?mapopp.get(oplin.opportunityId).totlanonnullcounts__c:0)+1);
   res=res+integer.valueof((mapopp.get(oplin.opportunityId).DeletedOpplineHold__c!=null?mapopp.get(oplin.opportunityId).DeletedOpplineHold__c:0));
  System.debug('DEleted count :'+(mapopp.get(oplin.opportunityId).DeletedOpplineHold__c));
  if(oplin.Item_Number__c==null)
  {

   res+=i;
   OpportunityLineItem  op=new OpportunityLineItem (id=oplin.id,Item_Number__c=res*10);
   UpdateOli.add(op);
   i++;
  }

}

if(UpdateOli.size()>0)
update UpdateOli;
        
 }//InsertingOppLineItems CLOSED


public static void UpdatingOppLineItems( OpportunityLineItem  [] OLit){
set<id> setopids = new set<id>();
List <OpportunityLineItem> UpdateOli = New List <OpportunityLineItem>();
for(OpportunityLineItem oli : OLit)
  {
    if(oli.opportunityId!=null)
    Setopids.add(oli.opportunityId);
 }

map<Id, Opportunity> mapOpp= new map<Id, Opportunity>([SELECT Id,DeletedOpplineHold__c,totlanonnullcounts__c from Opportunity Where Id IN :Setopids]);
integer i=0;

for(OpportunityLineItem oplin :OLit)
{
  integer res=integer.valueof((mapopp.get(oplin.opportunityId).totlanonnullcounts__c !=null?mapopp.get(oplin.opportunityId).totlanonnullcounts__c :0)+1);
  res=res+integer.valueof((mapopp.get(oplin.opportunityId).DeletedOpplineHold__c!=null?mapopp.get(oplin.opportunityId).DeletedOpplineHold__c:0));
  System.debug('**********==== :' +mapopp.get(oplin.opportunityId).DeletedOpplineHold__c);

//System.debug('R E S  :' +res);
  if(oplin.Item_Number__c==null)
  {
    res+=i;
    System.debug('R E S  :' +res);
    OpportunityLineItem  op=new OpportunityLineItem (id=oplin.id,Item_Number__c=res*10);
    UpdateOli.add(op);
    i--;
  }
 }

if(UpdateOli.size()>0)
update UpdateOli;

}

     

}

i am updating the records via Workbench, its throwing an error...

but i added to a list , and after that i am updating the list, not in the loop...pls give me the reply urgent pls..