Null Pointer Exception

In plain words: The Safe Navigation Operator ( ?. ) in Salesforce Apex evaluates the left-hand side of an expression. If that value is null , it immediately returns null instead of throwing a dreaded System.NullPointerException (NPE). Null pointer exceptions are among the most common run-time errors in Apex development. Traditionally, guarding against them required writing layers of verbose if (variable != null) checks. The safe navigation operator streamlines your code by letting you chain references and method calls safely on a single line.