trigger UpdateOpptyOnServiceupdate on Servic__c (after insert, after update)
{
Set<Id> oppid = new Set<Id>();
Map<Id,List<Service __c>> mpoppservice=new Map<Id,List<Service __c>>();
List<Opportunity> updatelist =  new list<Opportunity>();
String str =  null;
for(Service__c s:trigger.new)
{
if(s.Opportunity__c != null){
oppid.add(s.Opportunity__c);
}
List<Opportunity> opplist = [Select id,ServiceIncrement__c ,(Select id,Expired _Years__c from Service__r) From Opportunity where Id IN:oppid];
} 
For(Opportunity opp:opplist)
{
mpoppservice.put(opp.id,opp. Service__r);   
}
for(Opportunity oppty:opplist)
{
Integer i = 0;   
Id temp = oppty.id;
List<Service __c>  slist= mpoppservice.get(temp);   
if(slist.size()!=0)
{
for(Service__c s1: slist)
{
str =s1. Expired _Years__c;
if(str != '<1' && str != null)   
{
i = 2;
}
if(i==2)   
{
oppty.ServiceIncement __c = 'Yes';   
}
else
{
oppty.ServiceIncement __c = 'No';   
}   
updatelist.add(oppty);   
}   
}
}
      try
        {
          update updatelist;
         }catch(Exception e) 
         { 
          for(Service__c s : trigger.new)
          {
          Id opid= s.Opportunity__c;
          Opportunity op = [select id,name from Opportunity where id=:opid];
          s.addError('“Updating opportunity associated to this service,but could not because the required fields are missing on opportunity”');
          }  
       }
 }
}