Defensive Programming

In plain words: A Null Pointer Exception (NPE) happens when your code tries to open an empty box. If a variable or object points to null (nothing) and you attempt to read its fields, call its methods, or get its list items, Apex crashes because there is no data in memory to work with. In Salesforce development, the System.NullPointerException is one of the most frequent runtime runtime errors. Because Apex is strongly typed but initializes unassigned object references to null , any attempt to traverse unpopulated relationships, empty map lookups, or unassigned variables will throw an unhandled exception. Writing defensive, null-safe Apex keeps your applications stable and prevents unexpected transaction rollbacks.