For Loops

Apex supports three variations of the for loop:

The traditional for loop:
The list or set iteration for loop:
where variable must be of the same primitive or sObject type as list_or_set.
The SOQL for loop:
or
Both variable and variable_list must be of the same sObject type as is returned by the soql_query.

Curly braces ({}) are required around a code_block only if the block contains more than one statement.

Note

Each is discussed further in the sections that follow.

Force.com Apex Code Developer's Guide