Apex Developer Guide

Getting Started
Writing Apex
Data Types and Variables
Control Flow Statements
Conditional (If-Else) Statements
Loops
Do-While Loops
While Loops
For Loops
Traditional For Loops
List or Set Iteration for Loops
Iterating Collections
Classes, Objects, and Interfaces
Working with Data in Apex
Ways to Invoke Apex
Finishing Touches
Reference
Appendices
Glossary
PDF

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Traditional For Loops

The traditional for loop in Apex corresponds to the traditional syntax used in Java and other languages. Its syntax is:
1for (init_stmt; exit_condition; increment_stmt) {
2    code_block
3}
When executing this type of for loop, the Apex runtime engine performs the following steps, in order:
  1. Execute the init_stmt component of the loop. Note that multiple variables can be declared and/or initialized in this statement.
  2. Perform the exit_condition check. If true, the loop continues. If false, the loop exits.
  3. Execute the code_block.
  4. Execute the increment_stmt statement.
  5. Return to Step 2.
As an example, the following code outputs the numbers 1 - 10 into the debug log. Note that an additional initialization variable, j, is included to demonstrate the syntax: 
1for (Integer i = 0, j = 0; i < 10; i++) {
2    System.debug(i+1);
3}