Boeing Interview Question

Explain the four pillars of OOP (Abstraction, Encapsulation, Inheritance, Polymorphism). How is multiple inheritance achieved in Java? What is an abstract class, and how is it different from an interface? Explain the concept of constructors in Java. What are their types? How do you achieve runtime polymorphism in Java? Can you explain the concept of inner classes in Java? What is the use of super and this keywords? Data Structures and Collections What is the difference between ArrayList and LinkedList? How does a HashMap work internally in Java? What is the difference between HashMap, TreeMap, and LinkedHashMap? How does a Set ensure uniqueness of elements? What is the difference between Comparable and Comparator? Explain the difference between Iterator and ListIterator. How would you handle concurrent modifications in a collection?