NullPointerException

In plain words: Apex errors occur when your code encounters an unexpected situation—like reading an unassigned variable (Null Pointer), requesting a record that does not exist (Query Exception), violating validation rules (DML Exception), or hitting multi-tenant resource caps (Governor Limits). Salesforce Apex executes in a strongly typed, multi-tenant cloud runtime. While this architecture guarantees system security and shared resource availability, it also enforces strict execution rules. Encountering exceptions is part of everyday development, but understanding why they happen and how to resolve them defensively makes your code resilient, scalable, and production-ready.

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.