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.
Yes you can. You can create a private constructor for your class and you can create a static factory method which creates an instance of your object. In this method you can increment a counter, and throw an exception/return null, when the limit is exceeded.
use singleton pattern, there you maintain a global counter, which tracks the number of objects created and keeps a reference of them. Oncecounter exceeds, you do not allow to create any further object of your class.
yes you can. Give the responsibility of creating the object of the class, to the class itself (which takes care how many objects have been created) by making its constructor private and creating one public static method which creates the object of the class and returns to the client.
Minor note: the above code is not thread save. So in case you're accessing getObject from multiple threads (which usually happens when used within a webapplication) you'll need to add the synchronized keyword:
Else you'll might get more objects than wanted, if getObject gets executed at exactly the same time.