HCLTech Java Developer Interview Questions, Process, and Tips for Experienced

Java is a high-level, object-oriented programming language used to develop applications for various platforms.

• Java is platform-independent and can run on any device with a Java Virtual Machine (JVM)

• It is known for its security features and is commonly used for developing web and mobile applications

• Java is also used for developing enterprise-level applications and software tools

• Examples of Java-based applications includ

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.

Inheritance is a mechanism in which one class acquires the properties and behaviors of another class.

• It allows code reusability and saves time

• The class that is inherited is called the superclass or parent class

• The class that inherits from the superclass is called the subclass or child class

• The subclass can access all the public and protected methods and fields of the superclass

• Example: A Car class can inherit propertie

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 parent...read more

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

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.

Static or final method is a method that belongs to a class rather than an instance of the class.

• Static method can be called without creating an instance of the class.

• Final method cannot be overridden by a subclass.

• Static and final methods can be accessed using the class name.

• Example: Math.max() is a static method in the Math class.

• Example: String.toUpperCase() is a final method in the String class.

A collection is a group of objects that can be stored, manipulated, and retrieved as a single unit.

• Collections are used to store and manage groups of related objects.

• Java provides several built-in collection classes such as ArrayList, LinkedList, HashSet, etc.

• Collections can be used to perform operations like sorting, searching, filtering, and more.

• Collections can be generic or non-generic, depending on the type of obj

Yes, we can add string or integer value using map in Java.

• We can use put() method to add values to a map.

• For string values, we can use String as the value type.

• For integer values, we can use Integer as the value type.

• Example: Map map = new HashMap<>(); map.put("key", "value");

• Example: Map map = new HashMap<>(); map.put("key", 123);

Sleep method pauses the thread for a specified time, while wait method pauses the thread until notified.

• Sleep method is a static method of Thread class, while wait method is an instance method of Object class.

• Sleep method does not release the lock on the object, while wait method releases the lock and waits for notification.

• Sleep method can be interrupted by another thread, while wait method can only be interrupted by ...read more

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

SQL queries are used to retrieve, manipulate and manage data stored in relational databases.

• SQL stands for Structured Query Language

• Queries can be used to retrieve specific data from tables

• Queries can also be used to update, insert or delete data

• Examples of SQL queries include SELECT, INSERT, UPDATE and DELETE

• Understanding SQL is important for working with databases in Java

Abstraction is a concept of hiding implementation details while interface is a contract that defines the behavior of a class.

• Abstraction is achieved through abstract classes and methods

• Interface is a collection of abstract methods and constants

• Abstraction allows for flexibility in implementation

• Interface allows for multiple inheritance

• Abstraction is used for code reusability

• Interface is used for achieving polymorphism

Overloading is when multiple methods have the same name but different parameters. Overriding is when a subclass provides a different implementation of a method inherited from its superclass.

• Overloading is resolved at compile-time based on the method signature.

• Overriding is resolved at runtime based on the actual object type.

• Overloading is used to provide different ways to call a method with different parameters.

• Overrid...read more

The question is asking about the candidate's knowledge in Core Java, Spring, Hibernate, Spring Boot, SQL, and AngularJS.

• Core Java is the foundation of Java programming language.

• Spring is a popular framework for building Java applications.

• Hibernate is an ORM tool used for mapping Java objects to database tables.

• Spring Boot is a framework for building microservices.

• SQL is a language used for managing relational databases...read more

To connect 2 DBs from a Spring Boot application, configure multiple data sources and use JdbcTemplate or EntityManager for each DB.

• Configure multiple data sources in the application.properties file

• Create separate configuration classes for each data source

• Use JdbcTemplate or EntityManager to interact with each DB

• Specify the appropriate data source in the repository or service classes

Abstract method implementation is mandatory while default method is optional.

• Abstract method has no implementation in the abstract class and must be implemented by the subclass.

• Default method has a default implementation in the interface and can be overridden by the implementing class.

• Abstract method is used to enforce a contract while default method is used to provide a default behavior.

• Example: abstract method - publ...read more