Hello
        I am new in Salesforce .I created VF page controller class.In that I got the month year and want to convert month which is in Number format into string so for this I wrote the method Getmonth() but having error.Please help.
public class UploadCSVFileController
{
    private final Account acct;
    public id accountid{get;set;}
    public string Mon{get;set;}
    public string Yrs{get;set;}
    Public Period__c cp;
    Public String Monthinletter;
    Public String MonthWithZero;
    public UploadCSVFileController(apexpages.standardcontroller stdcontroller)
    {
        system.debug('Inside Constructor');
        acct=(Account)stdcontroller.getrecord();
        accountid=acct.id;
        System.debug('The account id'+accountid);
        Mon = ApexPages.currentPage().getParameters().get('mm');
        Yrs = ApexPages.currentPage().getParameters().get('yyyy');
        System.debug('The current month is:'+Mon);
        System.debug('The current year is:'+Yrs);   
        MonthWithZero=Mon.leftpad(2,'0');
        string monthyear=MonthWithZero+'-'+yrs;
        cp=[select id,name,Month_Year__c from Period__c WHERE name=:monthyear];
        system.debug(cp);
    }
    public String GetMonth(MonthWithZero)
    {
        if(MonthWithZero=='01')
        {
            Monthinletter='January';
            return Monthinletter;    
        }    
    }
}