HomeInterview QuestionTop Java Interview Questions

Top Java Interview Questions

a) What is JAVA?
Answer: Java is a high-level programming language and is platform-independent. It is a collection of objects and was developed by Sun Microsystems. There are a lot of applications, websites, and games that are developed using Java.

b) What are the features of JAVA?
Answer: Features of Java are mentioned below:
OOP concepts
Object-oriented
Inheritance
Encapsulation
Polymorphism
Abstraction

i) Platform independent: A single program works on different platforms without any modification.
ii) High Performance: JIT (Just In Time compiler) enables high performance in Java. JIT converts the bytecode into machine language and then JVM starts the execution.
iii) Multi-threaded: A flow of execution is known as a Thread. JVM creates a thread which is called the main thread. The user can create multiple threads by extending the thread class or by implementing the Runnable interface.

c) What is a singleton class in Java and how can we make a class singleton?
Answer: Singleton class is a class whose only one instance can be created at any given time, in one JVM. A class can be made singleton by making its constructor private.

d) Why are pointers not used in Java?
Answer: Java doesn’t use pointers because they are unsafe and increase the complexity of the program. Since Java is known for its simplicity of code, adding the concept of pointers will be contradicting. Moreover, since JVM is responsible for implicit memory allocation, thus in order to avoid direct access to memory by the user,  pointers are discouraged in Java.

e) What is a JIT compiler in Java?
Answer: JIT stands for Just-In-Time compiler in Java. It is a program that helps in converting the Java bytecode into instructions that are sent directly to the processor. By default, the JIT compiler is enabled in Java and is activated whenever a Java method is invoked. The JIT compiler then compiles the bytecode of the invoked method into native machine code, compiling it “just in time” to execute. Once the method has been compiled, the JVM summons the compiled code of that method directly rather than interpreting it. This is why it is often responsible for the performance optimization of Java applications at the run time.

f) What is Object-Oriented Programming?
Answer: Object-oriented programming or popularly known as OOPs is a programming model or approach where the programs are organized around objects rather than logic and functions. In other words, OOP mainly focuses on the objects that are required to be manipulated instead of logic. This approach is ideal for the program’s large and complex codes and needs to be actively updated or maintained.

g)  What are the main concepts of OOPs in Java?
Answer: Object-Oriented Programming or OOPs is a programming style that is associated with concepts like:
a) Inheritance: Inheritance is a process where one class acquires the properties of another.
b) Encapsulation: Encapsulation in Java is a mechanism of wrapping up the data and code together as a single unit.
c) Abstraction: Abstraction is the methodology of hiding the implementation details from the user and only providing the functionality to the users.
d) Polymorphism: Polymorphism is the ability of a variable, function or object to take multiple forms.

j) What is the final keyword in Java?
Answer: Final is a special keyword in Java that is used as a non-access modifier. A final variable can be used in different contexts such as:
Final variable- When the final keyword is used with a variable then its value can’t be changed once assigned. In case the no value has been assigned to the final variable then using only the class constructor a value can be assigned to it.

final method- When a method is declared final then it can’t be overridden by the inheriting class.

Final class- When a class is declared as final in Java, it can’t be extended by any subclass but it can extend other class.

i) Why are Java Strings immutable in nature?
Answer: In Java, string objects are immutable in nature which simply means once the String object is created its state cannot be modified. Whenever you try to update the value of that object instead of updating the values of that particular object, Java creates a new string object. Java String objects are immutable as String objects are generally cached in the String pool. Since String literals are usually shared between multiple clients, action from one client might affect the rest. It enhances the security, caching, synchronization, and performance of the application. 

- A word from our sponsors -

Most Popular

Leave a reply

Please enter your comment!
Please enter your name here

More from Author

Understanding API Calls

Written by Vikrant Chaudhary

TCS is accepting registrations for fresh MBA hiring

India’s largest Tech giant, Tata Consultancy Services (TCS) is accepting applications...

British Electric, One Moto India plans to hire, add people by 150%

British electric two-wheeler company, One Moto India has announced that it...

ICCS is all set to hire 1,000 employees in next 12 months

BPO firm, ICCS is hiring nearly 1,000 employees in the coming...

- A word from our sponsors -

Understanding API Calls

Written by Vikrant Chaudhary

TCS is accepting registrations for fresh MBA hiring

India’s largest Tech giant, Tata Consultancy Services (TCS) is accepting applications from management graduates who can join the company in the upcoming financial year 2022-23. The online registration process for this role is reopened for now. However, the last date to apply for the role is unknown. Students...

British Electric, One Moto India plans to hire, add people by 150%

British electric two-wheeler company, One Moto India has announced that it will be hiring and increasing manpower by 150% in the country, This will be the company’s first hiring drive in India. As of now, it has a workforce of 35 employees in India. And aims to take...

ICCS is all set to hire 1,000 employees in next 12 months

BPO firm, ICCS is hiring nearly 1,000 employees in the coming next 12 months. ICCS CEO Divij Singhal said, “We are now planning to expand our team and hire across roles to ensure the employees have the support they need so as to drive the organizational growth and...

Infosys hiring 50,000 freshers in FY23, offers salary hike this month

IT Tech giant, Infosys said that it has already hired 85,000 freshers both off-campus and on-campus in the financial year 2022 which ended on March 31. Infosys attrition rate reaches 27.7% in the March quarter, up from 25.5% in the December quarter, but the management was confident that...

Binance, the world’s largest cryptocurrency exchange, gets Abu Dhabi crypto nod

Binance Holdings Ltd. received in-principle approval from Abu Dhabi Global Market to operate as a broker-dealer in virtual assets. The world’s largest cryptocurrency exchange by trading volume still needs to complete the application process, Richard Teng, the company’s head for the Middle East and North Africa and a...

AWS Top Interview Questions

Question: What is AWS? Answer: AWS (Amazon Web Services) is a platform to provide secure cloud services, database storage, offerings to compute power, content delivery, and other services to help business level and develop. Question: What is the importance of buffer in Amazon Web Services? Answer: An Elastic Load Balancer...

Internship

Job description We are currently hiring for a Digital Marketing Internship part-timers to join our core team immediately.a) Are available for WFH internship,b) Can start the internship immediately,c) Are available for a duration of 2-3 monthsd) Final year college students can also apply for this internship Stipend: INR 2500/-Duration:...

TCS is all set to hire 1 Lakh freshers by March 31

India’s largest IT giant Tata Consultancy Services (TCS) could end Fiscal Year 2022 with fresher hiring of 100,000, the highest ever not just by the company in a financial year but also by any IT services player in India and multinationals. TCS has onboarded 77,000 freshers till December...

TCS expands its operations in New Jersey, all set to hire 1000 people by 2023

India’s largest Tech giant, Tata Consultancy Services (TCS) has announced recently, its plans to expand operations in New Jersey by hiring nearly 1,000 additional employees by the end of 2023. The plan is to meet the growing needs of customers to digitally transform their businesses. To nurture a...

Bharti Airtel to buy Vodafone 4.7% stake in Indus Towers for Rs3,000cr

Global telecommunications company Bharti Airtel has decided to acquire an additional 4.7 percent stake in Indus Towers from Vodafone Group, the company announced it on Friday. “The said acquisition purchase would be at an attractive price representing a significant discount typically available for such large block transactions. In addition,...

Mindtree is hiring| Service Desk Manager|Bangalore

Role description This opportunity is with Mindtree Ltd. for the position of Team Manager # Service Desk Operations. The role requires providing leadership, guidance, and support to existing L1 L2 line of support engineers. This is an opportunity in a well-stablished service desk for a major client of...