FollowUpTaskHelper.apex
Force.com Cookbook Sample Code
Chapter 4: Best Practices for Writing Apex - Controlling Recursive Triggers
To download all the code samples, access the Cookbook. - 
This Apex trigger is part of an example that shows how to control trigger recursion by using static member variables.
For this example to work properly, you first must define a custom checkbox field on Task. In this example, this field is named Create_Follow_Up_Task__c.
public class FollowUpTaskHelper {
// Static variables are local to the context of a Web request
// (or testMethod during a runTests call)
// Therefore, this variable will be initialized as false
// at the beginning of each Web request which accesses it.
private static boolean alreadyCreatedTasks = false;
public static boolean hasAlreadyCreatedFollowUpTasks() {
return alreadyCreatedTasks;
}
// By setting the variable to true, it maintains this
// new value throughout the duration of the request
// (or testMethod)
public static void setAlreadyCreatedFollowUpTasks() {
alreadyCreatedTasks = true;
}
public static String getFollowUpSubject(String subject) {
return 'Follow Up: ' + subject;
}
}
Sample code provided by salesforce.com. All rights reserved.