Top HCL Interview Questions and Answers

CTA

HCL Technologies, a prominent company in the field of IT services around the world, is based out of Noida, India. HCL has over 220,000 employees and pays a salary of ₹5 to ₹18 lakhs per year. HCL provides a variety of services such as IT consulting, software development, cyber security, etc., and is currently in hiring mode for various vacancies in different locations. Below we have provided some technical and behavioral questions that reveal the essence of your character.

Table of content

• Basic HCL Interview Questions for Freshers
• Intermediate HCL Technical Interview Questions
• Advanced HCL Interview Questions for Experienced

Most Frequently Asked HCL Interview Questions

1. Explain the concept of polymorphism in object-oriented programming.
2. How does garbage collection work in Java?
3. What is input-output (I/O) in C++?
4. Explain the concepts of OOPS?
5. What are the different cloud computing service models?
6. Explain the concepts of Static Keyword in Java?
7. What is the purpose of the Domain Name System (DNS)?
8. Explain the advantages of Relational Database Management System(RDBMS)
9. What is primary key explain with an example?

1. Explain the concept of polymorphism in object-oriented programming.

Polymorphism is a fundamental concept in object-oriented programming (OOP) that enables objects of different classes to be treated as objects of a common superclass. It refers to the ability of a single interface or method to be implemented in multiple ways. This is depending on the specific class or type of object involved. Polymorphism is a powerful concept in OOP that allows objects of different classes to be treated as instances of a common superclass.

2. How does garbage collection work in Java?

Garbage collection in Java is an automatic process that manages memory by freeing up space occupied by objects that are no longer in use. The Java Virtual Machine (JVM) keeps track of all objects created in the program. Once an object is no longer referenced by any part of the program, it becomes eligible for garbage collection to free up memory resources. The garbage collector identifies these unreachable objects and marks them for collection. During the garbage collection process, the JVM pauses the execution of the program and frees up the memory occupied by the marked objects. This reclaimed memory becomes available for future object allocations. Different garbage collection algorithms are employed to ensure efficient memory management and prevent memory leaks.

3. What is input-output (I/O) in C++?

In C++, input-output (I/O) refers to the process of exchanging data between a programme and its external environment. It involves showing output data on the screen or writing it to a file after reading input data from the user or a file. The standard library’s input and output streams, such cin and cout, are used to implement this capability. For the development of interactive and dynamic programmes, I/O activities are essential.

4. Explain the concepts of OOPS?

The four pillars of object-oriented programming (OOP) are encapsulation, inheritance, polymorphism, and abstraction.

Encapsulation: It is the bundling of data and methods into a single unit, called an object. Encapsulation provides data security by hiding the internal details of an object and allowing access only through defined interfaces. It helps in achieving code modularity and reusability.

Inheritance: It allows the creation of new classes (derived classes) from existing classes (base classes). Inheritance promotes code reuse and hierarchical organization of classes. Derived classes inherit properties and behaviors from their base classes, enabling the extension and specialisation of functionality.

Polymorphism: It refers to the ability of objects to take on many forms or respond differently based on the context. Polymorphism allows different objects to be treated as instances of a common superclass, enabling flexibility and extensibility. It is implemented through method overriding and method overloading.

Abstraction: It focuses on providing essential features while hiding unnecessary details. Abstraction helps in managing complexity by creating simplified models of real-world entities. It allows programmers to work at higher levels of abstraction and deal with objects and operations relevant to the problem domain.

5. What are the different cloud computing service models?

Cloud computing presents a diverse range of service models to accommodate various user requirements. The key service models include Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS).

• IaaS: It provides virtualized computing resources, such as virtual machines, storage, and networks, allowing users to manage and control the infrastructure.
• PaaS: It offers a platform for developing and deploying applications. It provides tools, libraries, and runtime environments,  to focus on application development without worrying about infrastructure management.
• SaaS: delivers software applications over the internet, eliminating the need for installation and allowing users to access applications directly through a web browser. The cloud provider handles all aspects, including infrastructure, platform, and software.

6. Explain the concepts of Static Keyword in Java?

In Java, the static keyword is used to declare class-level variables and methods that can be accessed without creating an instance of the class. Static members belong to the class itself rather than individual objects. They can be accessed using the class name and are commonly used for utility methods, constants, and shared data.

7. What is the purpose of the Domain Name System (DNS)?

The Domain Name System (DNS) serves as a crucial component of the internet infrastructure. Its purpose is to translate human-readable domain names into machine-readable IP addresses (such as 192.0.2.1) that computers use to communicate with each other. DNS acts as a decentralised, distributed directory that allows users to access websites, send emails, and perform various online activities without needing to remember complex numerical IP addresses. It plays a vital role in facilitating seamless and efficient communication across the internet.

8. Explain the advantages of Relational Database Management System(RDBMS)

Relational Database Management Systems (RDBMS) have several advantages:

Structured Data: RDBMS organises data into tables with predefined schemas, ensuring data integrity and consistency.

• Data Integrity: RDBMS supports constraints (e.g., primary keys, foreign keys) to maintain data integrity, preventing duplicate or inconsistent data.
• Data Relationships: RDBMS allows establishing relationships between tables using primary and foreign keys, enabling efficient data retrieval through joins.
• Data Security: RDBMS offers user authentication, access controls, and encryption mechanisms to protect data from unauthorised access.
• Backup and Recovery: RDBMS facilitates regular backups and provides mechanisms for data recovery in case of system failures or errors.
• Data Consistency: RDBMS enforces referential integrity, maintaining consistency across related data, and reducing data anomalies.

9. What is primary key explain with an example?

A primary key is a distinctive identifier that aids in uniquely identifying each record or row in a database table. It guarantees data integrity and acts as a point of comparison when linking records from several tables.

For instance, the “StudentID” column, which has a different integer for each student, might serve as the primary key in the “Students” database. This makes sure that no two students have the same identifier and makes data processing and retrieval simple.

10. What is the local and global variable in python?

Local and global variables are used in Python to store and access data within a program. 

A local variable is confined to a particular function or code block, ensuring it can only be accessed within that specific scope. On the other hand, a global variable is defined outside of any function and can be accessed from any part of the program. An suitable example would be : 

def my_function():
    x = 10  # local variable
    print(x)

my_function()
y = 20  # global variable
def function01():
    print(y)
function01()

11. What is cloud computing? How is it useful today?

Cloud computing is the transmission of computing services such as storage, processing power, and software applications through the internet. It enables consumers to get online and use these services whenever and wherever they choose. Several advantages of cloud computing, such as scalability, cost effectiveness, flexibility, and simplicity of access, make it helpful in today’s society. Without the need for significant infrastructure investments, it enables organizations and individuals to store and analyse massive volumes of data. It also enables them to interact remotely, and make use of powerful computer capabilities.

12. Explain the concept of method overriding in Java.

In the realm of Java, method overriding stands as a pivotal concept, enabling a subclass to furnish its personalized implementation of a method inherited from its superclass. When a method in the subclass has the same name, return type, and parameter list as the method in the superclass, it overrides the superclass method. This enables polymorphism, as the method called depends on the type of the object rather than its reference. Overriding allows customization and specialisation in subclasses while maintaining a common interface defined by the superclass.

13. What is the role of the 'final' keyword in Java?

The “final“ keyword in the Java programming language is used to specify constants, prevent method overriding, and limit class inheritance.

The “final” keyword makes constants, which maintain a single value throughout the programme, by making variables immutable. Because final methods cannot be overridden in subclasses, their behavior is maintained. Furthermore, when a class is marked as final, other classes cannot extend it, giving the user control over the class hierarchy. The “final” keyword encourages maintainability of the code, upholds immutability, and permits safe and efficient code execution.

14. Discuss the differences between shallow copy and deep copy in the context of object cloning.

Shallow copy and deep copy are two terms used to describe distinct ways to duplicate an object in the context of object cloning.

When an object is copied shallowly, the instance variable values from the original object are transferred to the new object. If the item, however, has references to other objects, the references—rather than the actual objects—are duplicated. This implies that the referred objects for the original object and the copied object will be the same.

In contrast, deep copy generates a new object and recursively copies each instance variable’s value, along with any objects that it references. This guarantees that every object that the cloned object refers to has a separate copy of it.

15. What are constraints in SQL?

Constraints in SQL are rules and conditions applied to the columns or tables in a database to maintain data integrity and ensure data consistency. There are several types of constraints:

• Primary Key: Ensures that each row in a table is uniquely identified by a specific column or combination of columns. It enforces the uniqueness and non-nullability of the key.
• Foreign Key: Establishes a relationship between two tables by referencing the primary key of one table in another table. It ensures referential integrity and maintains consistency across related tables.
• Unique: Ensures that a column or a combination of columns in a table contains unique values, excluding NULL values.
• Not Null: Ensures that a column cannot contain NULL values. It enforces the requirement for data to be present in that column.
• Check: Defines a condition that must be satisfied for the data in a column. It allows specifying a logical expression to validate the values inserted or updated in a column.
• Default: Assigns a default value to a column when no explicit value is specified during an insert operation.

16. What are some of the differences between C & C++?

C and C++ are both popular programming languages, but they have some key differences. Here are five points to help you understand their distinctions:

• Syntax: C follows a procedural programming paradigm with a simpler syntax, while C++ extends C by adding object-oriented programming (OOP) features, including classes and objects. This fosters code reusability and encourages modular programming practices.
• Compatibility: C++ is largely compatible with C, meaning most C programs can be compiled and run in a C++ environment. However, C++ introduces additional keywords and features that may cause compatibility issues when using a C compiler.
• OOP Support: One major difference is that C++ supports OOP concepts, such as encapsulation, inheritance, and polymorphism, while C does not. These features enhance code organization, maintainability, and extensibility.
• Standard Library: C++ provides an extensive standard library, which includes additional functionality beyond what’s offered in the C standard library. It includes containers, algorithms, input/output streams, and other utilities that simplify common programming tasks.
• Memory Management: C and C++ have different approaches to memory management. C allows manual memory allocation and deallocation using functions like malloc() and free(), while C++ introduces the concept of constructors and destructors to automate memory management using features like new and delete operators.

17. What are threads and explain it types?

Threads are lightweight execution units within a process that allow concurrent and parallel job execution. They enhance performance and responsiveness in programmed by enabling many sequences of instructions to run simultaneously.

Java uses various thread types, such as:

User Threads: The programme developer creates these, and users have control over them. User threads are maintained by the JVM and carry out specific tasks.

Daemon Threads: These are background threads that provide support to user threads., which are background threads. They are made to carry out background operations like garbage pickup, I/O operations, or other maintenance jobs. When all user threads have completed running, daemon threads are shut down.

18. What are Different types of joins?

SQL utilizes joins to merge rows from multiple tables based on a related column between them, allowing for effective data combination. There are several types of joins:

• Inner Join: Retrieves matching rows from both tables based on the specified join condition.
• Left Join: Retrieves all rows from the left (or “left-hand”) table and the matching rows from the right (or “right-hand”) table. If no match is found, NULL values are included for the columns of the right table.
• Right Join: Combines all rows from the right table with their matching rows from the left table. If no match is found, NULL values are included for the columns of the left table.
• Full Outer Join: Retrieves all rows from both tables, including unmatched rows from each side. NULL values are included for the columns where no match is found.

19. Describe the difference between a stack and a queue.

A stack and a queue are both fundamental data structures used in computer programming, but they differ in their principles of data organization and access.

A stack follows the Last-In-First-Out (LIFO) principle, meaning that the last element added is the first one to be removed. It resembles a stack of books, where the topmost book can be accessed or removed. The operations performed on a stack are push (add element) and pop (remove element). Stacks are commonly used for tasks like function calls, expression evaluation, and undo/redo functionalities.

A queue adheres to the First-In-First-Out (FIFO) principle, resembling a real-world queue. The element that enters first is the first one to be processed or removed. A queue supports two main operations: enqueue (add element at the end) and dequeue (remove element from the front). Queues are useful in scenarios such as task scheduling, event handling, and breadth-first search algorithms.

To summarise, a stack operates on the LIFO principle, while a queue operates on the FIFO principle. These data structures have distinct characteristics that make them suitable for different programming scenarios, depending on the desired ordering and access patterns of the data.

20. What are ACID Properties in DBMS?

ACID stands for Atomicity, Consistency, Isolation, and Durability. It is a set of properties that ensure reliability and integrity in database transactions (DBMS).

Atomicity: Atomicity guarantees that a transaction is treated as a single, indivisible unit of work. Either all the operations within a transaction are successfully completed, or none of them take effect. If any operation fails, the transaction is rolled back to its initial state.

Consistency: Consistency ensures that a transaction brings the database from one valid state to another. It enforces integrity constraints, business rules, and validation criteria during the transaction to maintain the correctness of data.

Isolation: Isolation ensures that concurrent transactions do not interfere with each other. Each transaction is executed as if it is the only transaction running, preventing interference and maintaining data integrity. Isolation levels, such as Read Uncommitted, Read Committed, Repeatable Read, and Serializable, provide varying levels of isolation.

Durability: Durability guarantees that once a transaction is committed, its changes are permanently saved and will survive any subsequent failures, such as power outages or system crashes. The changes are stored in non-volatile memory or persistent storage.

21. What is the difference between abstraction and encapsulation in Java?

Abstraction focuses on hiding unnecessary details and exposing only relevant information to the user. It allows us to create abstract classes and interfaces that define a common structure or behavior. By using abstraction, we can define a blueprint or template for objects, which can be extended or implemented by concrete classes.

Encapsulation, on the other hand, is about bundling data and methods together within a class and restricting direct access to the data from outside. It helps in achieving data security and integrity by controlling access through getter and setter methods. Encapsulation also allows for better code organization and maintenance.

In summary, abstraction deals with defining a higher-level view, while encapsulation deals with data hiding and ensuring controlled access to it.

// Abstraction
abstract class Shape {
    public abstract void draw();
}

// Encapsulation
class Circle extends Shape {
    private double radius;
    public double getRadius() {
        return radius;
    }

    public void setRadius(double radius) {
        this.radius = radius;
    }

    public void draw() {
        System.out.println("Drawing a circle with radius " + radius);
    }
}

public class Main {
    public static void main(String[] args) {
        Circle circle = new Circle();
        circle.setRadius(5.0);
        circle.draw();
    }
}

22. Explain the difference between a HashSet and a TreeSet.

HashSet and TreeSet are both implementations of the Set interface in Java, but they have some key differences in terms of behavior and performance.

HashSet:

• HashSet stores elements in a hash table using the hash code of the objects. It does not maintain any specific order of elements.
• Elements in a HashSet are not sorted. The order in which elements are stored can be different from the order in which they are added.
• HashSet allows null values and permits a single null element.
• It offers constant-time performance (O(1)) for basic operations like add, remove, contains, and size.
• HashSet is generally faster than TreeSet for most operations, especially for large data sets.
• Use HashSet when the order of elements is not important, and you need fast access and search operations.

TreeSet:

• TreeSet stores elements in a balanced tree structure based on the natural ordering or a custom comparator of the elements.
• Elements in a TreeSet are sorted in ascending order.
• TreeSet does not allow null values. All elements must be non-null and must be comparable.
• It offers log(n) time complexity (O(log n)) for basic operations.
• TreeSet is useful when you need the elements to be sorted and you require operations like finding the smallest or largest element.
• Additionally, TreeSet provides additional operations for range queries and finding elements greater than or less than a given value.

23. What is the difference between compiler, interpreter, and assembler?

A compiler, interpreter, and assembler are different types of software tools used in the process of programming.

A compiler is a program that translates the entire source code written in a high-level programming language into machine code or bytecode all at once. The resulting compiled code can then be executed directly by the computer’s hardware. Compilers optimize the code for efficiency, producing faster-running programs.

An interpreter executes the source code line by line, translating and executing each instruction as it encounters them. The interpreter does not produce a standalone executable file but directly runs the program. Interpreters are often used in scripting languages and allow for dynamic code execution, making them more flexible for tasks like debugging and prototyping.

An assembler, specifically used in low-level programming, translates assembly language code into machine code. Assembly language is a human-readable representation of machine code, using mnemonic instructions and symbols instead of binary digits. Assemblers perform a one-to-one mapping between assembly instructions and machine instructions, enabling direct interaction with the computer’s hardware.

24. Discuss the concept of software testing and different types of testing techniques?

Software testing is a crucial process in the software development lifecycle. It involves verifying and validating the functionality, performance, and quality of a software application. There are several types of software testing techniques used to uncover defects or errors in the software. The most common types include:

• Unit Testing: It involves testing individual components or units of the software to ensure their proper functionality.
• Integration Testing: It verifies the interaction between different modules or components of the software to ensure they work together seamlessly.
• System Testing: This type of testing examines the complete software system to evaluate if it meets the specified requirements.
• Acceptance Testing: It is performed to determine if the software meets the user’s requirements and is ready for deployment.
• Performance Testing: This technique checks how the software performs under different workload conditions, identifying bottlenecks and ensuring scalability.
• Security Testing: It assesses the software’s ability to protect against unauthorized access, data breaches, and other security vulnerabilities.
• Regression Testing: It ensures that changes or updates to the software do not introduce new defects or impact existing functionality.
• Usability Testing: This technique focuses on evaluating the software’s user-friendliness, intuitiveness, and overall user experience.

25. You are given a sorted array of integers [2, 4, 6, 8, 10, 12, 14, 16]. Write a Java program to find the index of a target element in the array using the binary search algorithm.

For example, if the target element is 10, what would be the output of the program?

public class BinarySearch {
    public static void main(String[] args) {
        int[] numbers = {2, 4, 6, 8, 10, 12, 14, 16};
        int target = 10;
        int index = binarySearch(numbers, target);
        if (index != -1) {
            System.out.println("Target element found at index: " + index);
        } else {
            System.out.println("Target element not found in the array.");
        }
    }

    public static int binarySearch(int[] array, int target) {
        int left = 0;
        int right = array.length - 1;
        while (left <= right) {
            int mid = (left + right) / 2;
            if (array[mid] == target) {
                return mid;
            } else if (array[mid] < target) {
                left = mid + 1;
            } else {
                right = mid - 1;
            }
        }