OpportunityTriggerHandler.cls

public class OpportunityTriggerHandler {

    // Method to create the Account-Opportunity Map
    public static Map<Id, List<Opportunity>> createAccountOpportunityMap(Set<Id> accountIds) {
        // Step 1: Query Opportunities with related Account Ids
        List<Opportunity> oppList = [
            SELECT Id, AccountId, Name
            FROM Opportunity
            WHERE AccountId IN :accountIds
        ];

        // Step 2: Initialize the Map
        Map<Id, List<Opportunity>> accountOppMap = new Map<Id, List<Opportunity>>();

        // Step 3: Organize Opportunities into the Map
        for (Opportunity opp : oppList) {
            if (!accountOppMap.containsKey(opp.AccountId)) {
                accountOppMap.put(opp.AccountId, new List<Opportunity>());
            }
            
            List<Opportunity> oppListForAccount = accountOppMap.get(opp.AccountId);
            oppListForAccount.add(opp);
        }

        // Return the map containing Account Ids as keys and lists of related Opportunities as values
        return accountOppMap;
    }

    // Method to check if an account has opportunities and add error if not
    public static void checkAccountHasOpportunities(List<Opportunity> opps) {
        // Create a set with the Account Ids from the opportunities
        Set<Id> accountIds = new Set<Id>();
        for (Opportunity opp : opps) {
            if (opp.AccountId != null) {
                accountIds.add(opp.AccountId);
            }
        }
        
        // Populate the map using the createAccountOpportunityMap method
        Map<Id, List<Opportunity>> accountOppMap = createAccountOpportunityMap(accountIds);
        
        // Step 4: Check if each opportunity's account has any opportunities in the map
        for (Opportunity opp : opps) {
            if (opp.AccountId != null && !accountOppMap.containsKey(opp.AccountId)) {
                opp.addError('The associated account does not have any opportunities.');
            }
        }
    }
}