This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
By reassigning it? This flag is probably meant as a means to switch debugging on and off quickly. It should probably be static and final, making it a constant. The developer then sets it to true when he needs to debug, and back to false when he deploys it.