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.
If you want to count the number of objects(boxes) created of Box class then static variable will be needed.
If color property of Box class needed then we can make color as non static as it will be in every object of Box class.