Trigger calculating total opportunity amount on account object

Count Total opportunities amount on account.

     First create one custom field on Account object = total_opp_amount (datatype = number);

trigger totaloppamount on opportunity(after insert,after update,after delete){

     map<id,list<opportunity>> accidopplistmap  = new map<id,list<opportunity>>();

     set<id> accids = new set<id>();

     list<opportunity> opplist = new list<opportunity>();

       if(trigger.isinsert || trigger.isupdate){

         for(opportunity opp : trigger.new){

           if(opp.accountid != null){

          accids.add(opp.accountid);

         }

        }

        }

       if(trigger.isdelete){

         for(opportunity opp : trigger.old){

         if(opp.accountid != null){

            accids.add(opp.accountid);

         }

         }

       }   

     if(accids.size()>0){

        opplist = [select amount,Accountid from opportunity where Accountid in : accids];

        for(opportunity op : opplist){

           if(op.amount != null){

           if(!accidopplistmap.containskey(op.accountid)){

                accidopplistmap.put((op.accountid),new list<opportunity>());

           }

           }

               accidopplistmap.get(op.accountid).add(op);

        }

       list<account> acclist = new list<account>();

       acclist = [select total_opp_amount__c from account where id in :accids];

       for(account acc: acclist){

          list<opportunity> templist = new list<opportunity>();

          templist = accidopplistmap.get(acc.id);

          Double totalopamount = 0;

           for(opportunity o: templist){

            if(o.Amount!= null){

               totalopamount += o.Amount;

            }

          }

          acc.total_opp_amount__c = totalopamount;

        }

        update acclist;

     } 

     }