<!-- START : VF PAGE -->

<apex:page standardController="Account" extensions="AccountExtensions">
  <apex:form > 
      <apex:pageblock title="Account Owner From Standard Controller">
          <apex:pageblockSection >
              <apex:outputfield label="Account Owner" value="{!Account.Owner.Name}"/>
          </apex:pageblockSection>
      </apex:pageblock>
      <apex:pageblock title="Account Owner From Extensions">
          <apex:pageblockSection >
              <apex:outputText label="Account Owner" value="{!accountOwner}"/>
          </apex:pageblockSection>
      </apex:pageblock>
  </apex:form>
</apex:page>

<!-- END : VF PAGE -->


//<!-- START: Extensions Class -->

public with sharing class AccountExtensions {
    
    public Account oAccount ;
    
    public AccountExtensions(ApexPages.StandardController stdController){
        oAccount = [SELECT Id, Owner.Name FROM Account WHERE Id =: ApexPages.CurrentPage().getParameters().get('Id')] ;
    }
    public String accountOwner {
        get{
            if(accountOwner == null){
                accountOwner = oAccount.Owner.Name ;
            }
            return accountOwner ;
        }
        private set ;
    }
}

//<!-- END: Extensions Class -->