Question d’entretien chez TransUnion

1.What is Inheritance? How to implement it in Java? 2.What is Polymorphism? How to implement it in Java? 3.How are abstract classes different from interfaces? 4.How are functions different from methods in Java? What is a primary key? What is a unique key? How are these two different? What are the different types of join used in SQL? Explain them. find perfect number in a given range