Need help on apex logic

Question

I'm stuck on retrieving account for particular orders. My final requirement is to build a list with all orders details and the account it belongs to. So here's my story so far...

I have 2 new custom objects, SUBSCR_SYSTEMS__c and orders__c. SUBSCR_SYSTEMS__c holds the legacy ids. I need to a build a list of orders comparing few fields in SUBSCR_SYSTEMS__c.

1. lst_PartnersAcc contains partner ids as customer legacy numbers and it's related accounts (which is my target to display and I'm unable to).

2. orders contains a list of orders that I'm displaying on VF. But here, account__c is empty. So it need to be updated programmatically with values from lst_PartnersAcc.

   public class OrderTrackingPartners{
   
   public List<orders__c> orders {get; set;}
   public OrderTrackingPartners() {   
   }
   
   
     public list<orders__c> getstart() {
    // territory
   
    Map<Id,UserTerritory> UserTerritoryCurrentUserMap = new    Map<Id,UserTerritory>([Select u.UserId, u.TerritoryId, u.IsActive, u.Id  From UserTerritory u Where u.isActive=true and u.userId =: UserInfo.getUserId()]);
   set<Id> TerritoryIdSet = new set<Id>();
   for(UserTerritory ut:UserTerritoryCurrentUserMap.values())
   {
     TerritoryIdSet.add(ut.TerritoryId);
   }    
   
   list<Group> map_group = [Select Id, RelatedId from Group where Type='Territory' AND RelatedId IN : TerritoryIdSet];
   
   
   //get legacy customer number from logged in user info
   
   //***Get Partner ids ***//
    List<SUBSCR_SYSTEMS__c> lst_PartnersAcc = [SELECT LEGACY_CUST_NUM__c,Account__c
                                            FROM SUBSCR_SYSTEMS__c WHERE Account__c IN                                                  
                                            (Select  AccountId from AccountShare where ( UserOrGroupId IN : map_group OR  UserOrGroupId =:UserInfo.getUserId()) AND RowCause IN ('Territory', 'TerritoryManual', 'TerritoryRule'))
                                            ];
   
   Set*String*tempList = new Set*String*();
   //Set <Id>tempListAcc = new Set<Id>();
    for(SUBSCR_SYSTEMS__c s : lst_PartnersAcc) {
   tempList.add(s.LEGACY_CUST_NUM__c);
   // tempListAcc.add(s.Account__c);
    }
   
   //***Retreive all orders***//
   
    List<orders__c> orders =[SELECT Orders__c,id, customer_order_number__c,name,order_no__c,account__c,account__r.name,number_of_line_items__c,number_of_items_open__c,lines_items_shipped__c,number_of_items_delivered__c,order_date__c,Bill_to__c,Payer__c,Ship_To__c,Sold_to__c FROM orders__c   
                            WHERE  Bill_to__c IN: tempList OR
                                   Payer__c IN: tempList OR 
                                   Ship_To__c IN: tempList OR
                                   Sold_to__c IN: tempList
                                ]; 
   
    if(orders.size()>0) {            
       if(String.isNotBlank(orders[0].Ship_To__c))   { 
       List<SUBSCR_SYSTEMS__c> Acc=[SELECT Account__c FROM SUBSCR_SYSTEMS__c where LEGACY_CUST_NUM__c=:orders[0].Ship_To__c];
   
   
       for(orders__c go: orders){
       go.account__c=Acc[0].Account__c;
       }
   
          system.debug('-----finale-------'+Acc);
      } 
   } 
   
   return orders;                                
   }                                
   
   }
   

From the VF output, I can see that correct orders are being retrieved, but I'm unable to get the associated accounts to a particular order.

Any help or suggestion would be great! Thanks

EDIT after @mihai's suggestion..

     Map<String,orders__c> mapOfOrders = new Map<String,orders__c>();

     List<orders__c> orders = [SELECT Ship_To__c,Orders__c,id, customer_order_number__c,name,order_no__c,account__c,account__r.name,number_of_line_items__c,number_of_items_open__c,lines_items_shipped__c,number_of_items_delivered__c,order_date__c,Bill_to__c,Payer__c,Sold_to__c FROM orders__c   
                             WHERE  Bill_to__c IN: tempList OR
                                    Payer__c IN: tempList OR 
                                    Ship_To__c IN: tempList OR
                                    Sold_to__c IN: tempList
                                 ]; 
   for(orders__c order : orders){
    mapOfOrders.put(order.Ship_To__c, order);
}
  List<SUBSCR_SYSTEMS__c> subList = [Select Account__c from SUBSC_SYSTEMS__c Where LEGACY_CUST_NUM__c=: orders.keySet()];
for(SUBSCR_SYSTEMS__c sub : subList){
   if(String.isNotBlank(orders.get(sub.LEGACY_CUST_NUM__c))){
       orders.get(sub.LEGACY_CUST_NUM__c).Account__c=sub.Account__c ;
   //since my aim is to copy account__c from SUBSCR_SYSTEMS__c to orders__c. Both has same field name.
   }
}

ERROR: Error: Compile Error: Method does not exist or incorrect signature: [List].keySet(). As far as I know keySet accepts a set of orders.

Answer 1

    Map<String,orders__c) mapOfOrders = new Map<String,orders__c>();
    Set<Id> ordersIds = new Set<Id>();

    List<orders__c> orders = [SELECT Ship_To__c,Orders__c,id, customer_order_number__c,name,order_no__c,account__c,account__r.name,number_of_line_items__c,number_of_items_open__c,lines_items_shipped__c,number_of_items_delivered__c,order_date__c,Bill_to__c,Payer__c,Sold_to__c FROM orders__c   
                                 WHERE  Bill_to__c IN: tempList OR
                                        Payer__c IN: tempList OR 
                                        Ship_To__c IN: tempList OR
                                        Sold_to__c IN: tempList
                                     ]; 
    for(orders__c order : orders){
        mapOfOrders.put(order.Ship_To__c, order);
        ordersIds.add(order.Id);
    }
    List<SUBSCR_SYSTEMS__c> subList = [Select Account__c from SUBSC_SYSTEMS__c Where LEGACY_CUST_NUM__c IN :ordersIds];
    for(SUBSCR_SYSTEMS__c sub : subList){
       if(String.isNotBlank(mapOfOrders.get(sub.LEGACY_CUST_NUM__c))){
            sub.Account__c =  mapOfOrders.get(sub.LEGACY_CUST_NUM__c).Account__c;
       }
    }

Let me know if it helps, basically looped through the orders and put them into a map and the key of the map is the Ship_To__c which I'm using it further to get the relevant information in the other for loop.