HCLTech Java Developer Interview Questions and Answers for Experienced

OOPs is a programming paradigm based on the concept of objects.

• OOPs stands for Object-Oriented Programming.

• It focuses on creating objects that contain both data and functions.

• Encapsulation, Inheritance, Polymorphism, and Abstraction are the four main pillars of OOPs.

• Java is an OOPs language.

• Example: A car is an object that has properties like color, model, and functions like start, stop, and accelerate.

Java is used for developing desktop, web, mobile, and enterprise applications.

• Desktop applications like media players, IDEs, and scientific applications

• Web applications like e-commerce websites, social media platforms, and banking portals

• Mobile applications for Android devices

• Enterprise applications like customer relationship management systems and supply chain management systems

Polymorphism is the ability of an object to take on many forms.

• Polymorphism allows objects of different classes to be treated as if they are of the same class.

• It is achieved through method overriding and method overloading.

• Example: A parent class Animal can have child classes like Dog, Cat, and Bird. All these child classes can have their own implementation of the method 'makeSound', which is overridden from the p...read more

There are four main OOPs concepts in Java: Abstraction, Encapsulation, Inheritance, and Polymorphism.

• Abstraction: Hiding implementation details and showing only necessary information.

• Encapsulation: Wrapping data and methods into a single unit and restricting access to them.

• Inheritance: Acquiring properties and behavior of a parent class by a child class.

• Polymorphism: Ability of an object to take many forms and per...read more

System.out.println is a Java statement used to print output to the console.

• System is a class in Java's core library.

• out is a static member of the System class.

• println is a method of the PrintStream class.

• It is used to print output to the console.

• It adds a newline character at the end of the output.

Join in SQL is used to combine rows from two or more tables based on a related column between them.

• Join is used to retrieve data from multiple tables in a single query

• Types of join include inner join, left join, right join, and full outer join

• Join condition is specified using ON keyword

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column

• Join can also be used with subqueries