how to call helper class function in magento ?[SOLVE]

simple create a class file under like D:\xampp\htdocs\FE2U\app\code\local\Rename\User\Helper/Getdata.php
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class Rename_Rename_Helper_Getdata extends Mage_Core_Helper_Abstract

{




    public function getUserName()

    {

        if (!Mage::getSingleton('customer/session')->isLoggedIn()) {

            return '';

        }

        $customer = Mage::getSingleton('customer/session')->getCustomer();

        return trim($customer->getName());

    }



   



}

----------------------------------call in Controller page -----------------------------------------------

Mage::helper('User/Getdata')->getUserName();

Default helper class is Data and this defaults to Yourmodule/Helper/Data.php

Mage::helper('User')->getUserName();