What is a deadlock? Explain. What is Spring framework? HTTP is a stateless protocol. How is HttpSession implemented then? What is String.intern()? My Hashtable returns in constant time for most keys but for certain ones it takes a while. What is wrong? Explain volatile keyword. Is volatile keyword thread-safe? Explain a few design patterns. Name a few methods from Object class and tell what do they do. There is an integer array which only contains 1s, 2s and 3s. How will you sort it? What value has UML added in your projects? Java API says if you override equals method you should override hashCode too. Why?