Apex Developer Guide

Apex Developer Guide
Release Notes
Getting Started with Apex
Writing Apex
Data Types and Variables
Control Flow Statements
Classes, Objects, and Interfaces
Classes
Interfaces
Keywords
Annotations
Classes and Casting
Differences Between Apex Classes and Java Classes
Class Definition Creation
Namespace Prefix
Using the System Namespace
Using the Schema Namespace
Namespace, Class, and Variable Name Precedence
Type Resolution and System Namespace for Types
Apex Code Versions
Lists of Custom Types and Sorting
Using Custom Types in Map Keys and Sets
Working with Data in Apex
Document Your Apex Code
Running Apex
Debugging, Testing, and Deploying Apex
Apex Reference
Appendices
PDF

Note: This release is in preview. Features described here don’t become generally available until the latest general availability date that Salesforce announces for this release. Before then, and where features are noted as beta, pilot, or developer preview, we can’t guarantee general availability within any particular time frame or at all. Make your purchase decisions only on the basis of generally available products and features.

Type Resolution and System Namespace for Types

Because the type system must resolve user-defined types defined locally or in other classes, the Apex parser evaluates types as follows:
  1. For a type reference TypeN, the parser first looks up that type as a scalar type.
  2. If TypeN is not found, the parser looks up locally defined types.
  3. If TypeN still is not found, the parser looks up a class of that name.
  4. If TypeN still is not found, the parser looks up system types such as sObjects.

For the type T1.T2 this could mean an inner type T2 in a top-level class T1, or it could mean a top-level class T2 in the namespace T1 (in that order of precedence).