NullPointerException de-reference a null object in Apex code trigger

Resolve NullPointerException

The solution is to make sure the Object and/or the Attribute to be used is not null. In this example, the code needs to be modified as follows:

Account newAccount = accountMap.get(oldAccount.Name);

        if (newAccount != null) 

          if (newAccount.Site != null) 

            i = newAccount.Site.length();

Exception handling routine

Account newAccount = accountMap.get(oldAccount.Name);

        try {

             i = newAccount.Site.length();

            }
            catch (System.NullPointerException e) {

            e1 = e; // can be assigned to a variable to display a user-friendly error message

        }

For more information on handling exceptions, check the Apex Language Reference, under "Using Exception Methods," or "Using Exception Variables."

For more information on initializing variables, look under Chapter 2, "Language Constructs", in the topics "Variables", and "Case Sensitivity".