Hello... this is my first attempt at a custom controller. The purpose is to get  user and contact information from a Custom Controller based on the User object. I recieve the following error:

'System.QueryException: List has no rows for assignment to SObject'

 at the ' private final User user; ' statement. This was pretty much out of the Apex Developer guide for Custom Controllers  but I'm obviously missing something because I can't get past this error. 

Thanks for looking.

Regards,

public class CPcontroller {
private final User user;
private final Contact contact;
private final Case c;
public CPcontroller() {


user = [select id,Name,ContactId,TimeZoneSidKey,Account_Sharing__c, Title, CompanyName,Phone,Extension,Fax,MobilePhone,
Email,Street,City,State,Country,PostalCode,CurrencyIsoCode from User where Id =
:ApexPages.currentPage().getParameters().get('Id') ];
contact = [select id, Name,Email,Phone,Fax,MailingStreet,MailingCity,MailingState,MailingPostalCode,MailingCountry,Title,
ContactAccountName__c from Contact where Id = :user.Contactid] ;

}

public User getUser() {
return user;
}

public Contact getContact() {
return contact;

}
public PageReference save() {
update user;
update contact;
return null;
}


}