Batch processing in Apex

If you want to run large jobs in other words if you want to process  million of records in asynchronous way then batch apex will do the job for you. 

Your class must implement Database.Batchable interface and should implement following method

• Start
• Execute
• Finish

Let create a simple Batch demo. Let say you want to append name of every account with '-ACC' and you have over 10,000 accounts then batch apex will do the job for you. Sorry this seems like a bad example but will make you understand the concept in a very simple way.

Create 2 class 

• BatchAccount
• AccountDML

global class BatchAccount implements Database.Batchable<sObject>
{
    global Database.QueryLocator start(Database.BatchableContext BC)
    {
        string Query = 'select id, name from account';
        return Database.getQueryLocator(query);
    }
    
    global void execute(Database.BatchableContext BC, List<account> acc) 
    {
        AccountDML.ProcessAccount(acc);
    }
    
     global void finish(Database.BatchableContext BC)
     {
         system.debug('Finished processing');
         // You can also send email as well if thats what you want
         
     }
    
}

public class AccountDML 
{
   public static void ProcessAccount (list<account> act)
   {
       list<account> actlist = new list<account>(); 
       try
       {
           for(account a : act)
           {
               a.name = a.name+'ACC';
               actlist.add(a);
               
           }
          database.SaveResult[] sr=  database.update(actlist);
       }
       catch(exception ex)
       {
           system.debug(ex.getMessage());
       }
       
       
       
   }
}

For running the batch mode you go to run your code something like shown below

BatchAccount  ba = new BatchAccount ();
database.executeBatch(ba,2);

Tada there you are. Now you  are expert in writing batch apex. Well done :)