Frage im Vorstellungsgespräch bei Cognizant

Explain the difference between == and .equals() in Java. (== checks reference equality, .equals() checks value equality). What are the differences between JDK, JRE, and JVM? Why is Java platform-independent? Explain the four pillars of OOP (Encapsulation, Inheritance, Polymorphism, Abstraction) with examples. Difference between an abstract class and an interface? Why are Strings immutable in Java? What are Collections in Java? Difference between ArrayList and LinkedList or HashMap and Hashtable? Explain multithreading and the difference between a process and a thread. What is a Singleton class and how do you implement it? Explain the final, finally, and finalize keywords.