BT Group Senior Java Developer interview questions

1) There is a class in which i declare 2 instance variables. A map and a string. Initialize both. Then, pass both of them to a method and change the values. What will be the value of map and string before and after calling the method. 2) Dynamic Polymorphism. All the variants(Object of child, reference of parent etc etc). If the methods are static , how does DP work? 3) Typecasting. How does it work? 4) Immutable classes. How do you initialize it? 5) When do you prefer Interfaces and when abstract class. Prepare well for this question. They confuse you a lot. 6) Overloading with different arguments. 7) Instantiating an abstract class. There is an abstract class and other normal class extends the abstract class. In constructor it calls , super(this). What happens?

Java- OOPS, mutithreading, collections, strings, serialization DS- Tree, LinkedList DB- Some sql queries