Execution enters IF loop, even if the condition is not satisfied

Question

if(User.FirstName != NULL && User.MiddleName != NULL && User.LastName != NULL) {

User usr = [SELECT FirstName,MiddleName,LastName FROM User WHERE 
                                       id=:userinfo.getuserid()];

System.debug('from if   FirstName  '+usr.FirstName);
System.debug('from if   MiddleName  '+usr.MiddleName);
System.debug('from if   LastName  '+usr.LastName);
}

Even, if FirstName & MiddleName are NULL, execution enters if loop. Why does this happen?

Answer 1

Visualforce has a global variable $User, there is no equivalent in apex.

In your code, Object.FieldName will return API name of field on the object with type Schema.SObjectType, you have to query User in an Object or list before the IF loop and use that for comparison.