Getting error in batch apex on runtime

Question

I am getting runtime error with null pointer exception.In the debug logs it is showing value of idofacc is null. Please help its urgent.

Batch Apex:

global class testbatch implements Database.Batchable<SObject>, Database.Stateful {
    global List<Id> idofacc;
    global Account[] updates;
    global testbatch(){
    List<Id> idofacc = new List<Id>();
    Account[] updates = new Account[] {};
    }
    public Database.QueryLocator start(Database.BatchableContext context) {
        return Database.getQueryLocator([select Id from Account order by Name]);
    }

    public void execute(Database.BatchableContext context, List<Account> scope) {


        for (AggregateResult ar : [
                select  Account__c a, count(Id) c
                from Contact_Point__c
                where Status__c=true and Account__c in :scope
                group by Account__c
                ]) {
           set<id> ids=new set<id>();
           for(contact com:[SELECT id,firstname,AccountId FROM Contact where accountid =:(Id)ar.get('a')])
           {
            ids.add(com.id);
            }
        Integer dec=[Select count() from Contact_Point__c
                        where Status__c=true and Contact__c in :ids];
        updates.add(new Account(id=(Id)ar.get('a'),No_of_active_CP_on_Account__c =(integer)ar.get('c'),No_of_active_CP_on_Contact__c =dec));
        idofacc.add((Id)ar.get('a'));
                }
        update updates;
        System.debug('value of update :::: '+updates);



        }



    public void finish(Database.BatchableContext context) {

       Id templateId = [Select id from EmailTemplate where name=:'test template'].id;
        System.debug('value of template ::::: '+templateId);
        Map<Id, String> emailMap = new Map<Id, String>();
        System.debug('value of ID ::: '+idofacc);
        List<Account> ls = [select Id,OwnerId,Name FROM Account where Id in :idofacc];
        List<String> ownid = new List<String>();
        List<String> accName = new List<String>();
        System.debug('value of ID ::: '+ls);
        for(Account acc: ls){
         ownid.add(acc.OwnerId);
         accName.add(acc.Name);
        }
         System.debug('value of accName ::: '+accName);
        System.debug('value of ownid ::: '+ownid);
        List<User> mailid = [Select Id,Email FROM User WHERE Id in :ownid];
            for(User u :mailid){
                emailMap.put(u.Id, u.Email);
            }
        System.debug('value of emailMap ::: '+mailid);

        System.debug('value of emailMap ::: '+emailMap.values());

        for(Integer i = 1;i<updates.size();i++){
            for(String s :accName){
            Account CPonAccount = updates[i];
            Decimal abc = CPonAccount.No_of_active_CP_on_Account__c;
            Decimal pqr = CPonAccount.No_of_active_CP_on_Contact__c;
            //String accId = CPonAccount.Id;
            //String AccNm = [SELECT Name FROM Account where Id = : accId];
            System.debug('value of CPonAccount ::: '+CPonAccount);
            System.debug('value of abc ::: '+abc);
            System.debug('value of pqr ::: '+pqr);
            Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
            mail.setTargetObjectId(CPonAccount.Id);
            mail.setToAddresses(emailMap.values());
            mail.setSubject('Updated Count of Contact Points for ' + s);
            mail.setSaveAsActivity(false);
            mail.setTemplateId(templateId);
            mail.setPlainTextBody('Number of active contact points on Account ' + abc +'\n'+'Number of active contact points on Contact '+ pqr);
            Messaging.sendEmail(New Messaging.SingleEmailMessage[]{mail});

            }
        }


    }
}

Answer 1

When declaring variables you can initialize them in the declaration.

You attempted to initialize them in the testbatch() method but you never called it so that variables / properties were always null

change to:

global List<Id> idofacc = New List<ID>();
global Account[] updates = New List<Account>();

remove

global testbatch(){
    List<Id> idofacc = new List<Id>();
    Account[] updates = new Account[] {};
    }