An important Case

updating data of one list by getting value from another list we will need a map for this case(2nd ''for loop'')

public void test(list<Contact> triggerNew)

    {

    Set<ID> stID=new Set<ID>();

    if(triggerNew.size()>0 && triggerNew!=null)

    {

    for(Contact obj:triggerNew)

    {

      stID.add(obj.accountid);

    }

    }

    List<Account> lstAccount=new List<Account>();

    Map<id,String> mp=new Map<id,string>();

    lstAccount=[Select id,name from Account where id in:stID];

   for(Account ob:lstAccount)

   {

       mp.put(ob.id,ob.name);

       

   }

    for(Contact objj:TriggerNew)

    {

          objj.Title=mp.get(objj.accountid)+'Krrish';

    }

   

    }