This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
The fact that abstract classes have constructors does not remove the fact that you cannot instanciate an abstract class. You wrongly assume that you can call "new" on any class having a constructor. The golden rule is : you can't instanciate abstract classes. Now, you should think of what would happen with the following code : HelloWorld hw = new ManageAbstract();