Top 45 Infosys Interview Questions for Java Developer
Are you preparing for a job interview at Infosys as a Java developer? As one of the largest IT companies in India, Infosys is known for its rigorous recruitment and selection process to hire the best employees for the company. To help you ace your interviews and secure your dream job, we have curated a comprehensive list of the top Infosys interview questions for Java developers. This guide is packed with valuable insights and tips that will equip you with the knowledge and confidence necessary to navigate the interview process successfully. So, let’s dive right in and get you one step closer to your career goals!
Infosys Java Developer Interview Questions for Freshers
Here are the most recently asked Infosys interview questions for Java developers who have little or relevant work experience
Q1. Explain the term Java.
Answer: Java is an object-oriented programming language developed by Sun Microsystems. It is a portable, platform-independent, simple, and secure language that enables developers to write code once and run it anywhere.
Q2. Define polymorphism.
Answer: Polymorphism refers to having many forms. In Java, it allows objects of different classes to be treated as if they belong to a common class by ensuring that different classes can share common methods. The two types of polymorphism in Java are compile-time polymorphism and runtime polymorphism.
Q3. Define a class.
Answer: A class is a blueprint or prototype from which objects are created. It represents a set of properties or methods that are common to all objects of one type.
Q4. Explain the term encapsulation.
Answer: Encapsulation refers to the bundling of related fields and methods into a single class. It prevents external access to an object’s state data except through the defined methods.
Q5. What does method overriding mean?
Answer: Method overriding means having two methods with the same name and parameters (i.e., method signature) but different implementations in parent and child classes. This allows polymorphism as child classes can provide their implementations for the method.
Q6. Define the term inheritance.
Answer: Inheritance represents the parent-child relationship between two classes, where one class(child) acquires the properties and methods from another class(parent). This leads to the reusability of code.
Q7. What are some features of Java?
Answer: Some key features of Java are:
- Platform Independent: Java code can be run on any device or operating system, thanks to the “Write Once, Run Anywhere” principle, which is facilitated by the Java Virtual Machine (JVM).
- Object-oriented Programming: Java follows the object-oriented programming paradigm. This enables the creation of modular and reusable code through the use of classes and objects.
- Robust and Secure: Java provides strong memory management, exception handling, and a robust set of libraries. These features ensure the development of secure and reliable applications.
- Automatic Memory Management: Java’s automatic memory management, also known as garbage collection, handles memory allocation and deallocation automatically. This reduces the risk of memory leaks and makes memory management more efficient.
- Architectural Neutrality and Portability: Java is designed to be platform-independent, allowing programs to run on any architecture without modification. This feature enhances portability across different systems.
- Supports Concurrency and Multithreading: Java supports concurrency and multithreading, allowing for the concurrent execution of multiple tasks and enhancing performance. It efficiently manages multiple threads, enabling parallel processing.
- Rich API and Vast Community: Java provides a comprehensive library of pre-built classes and methods (API), facilitating development. Its large community ensures a wealth of resources, support, and third-party libraries for developers.
Q8. Define an Object.
Answer: An object is an instance of a class that has its state, behavior, and identity. It is a basic runtime entity with a state and defined functionality.
Q9. What do you understand by abstract class?
Answer: An abstract class can only be used as a base for subclasses but cannot be instantiated. It contains abstract methods with only declarations but no implementations. Subclasses need to provide implementations for the abstract methods.
Q10. Explain the terms local variable and instance variable.
Answer: Local variables are declared inside a method, constructor, or block. They exist only within the scope where they are defined. Instance variables are variables declared within a class but outside any method. These variables represent the state of that particular object.
Q11. Explain the term Interface.
Answer: An interface defines a blueprint or contract that classes must follow without providing any implementation for the methods declared in the interface. It contains only constants, abstract methods, default methods, and static methods.
Q12. Explain the term Constructor.
Answer: A constructor is a special method that has the same name as the class itself. It is used to initialize the state of an object when it is created. Java automatically invokes the constructor whenever an object is created from a class.
Q13. Explain how Java aids high performance.
Answer: Java improves performance by use of a ‘Just-In-Time’ compiler, improved garbage collection algorithms, multi-threading support, etc. Its architecture provides platform independence, security, high performance, etc.
Q14. Explain the Object-Oriented Programming (Oops) concepts in Java.
Answer: The Java programming language follows the principles of OOP. It allows developers to create objects, define their behavior, and interact with them to build efficient software applications. The key OOPS concepts in Java are as follows.
- Abstraction: It refers to the process of hiding complex implementation details from users by providing simpler interfaces for them to interact with.
- Encapsulation: This involves including data (variables) and methods (functions) into a single unit called an object.
- Inheritance: This is a mechanism where one class can inherit properties (attributes/fields) and behaviors (methods/functions) from another parent class.
- Polymorphism: This refers to having multiple forms/interfaces for the same function/method depending on different input parameters or contexts.
Q15. Mention some popular Java IDEs (Java Integrated Development Environments).
Answer: Some popular Java IDEs are:
- Eclipse: This is an open-source IDE that offers support for various programming languages, including Java.
- NetBeans: This is another popular open-source IDE designed specifically for Java development. Its intuitive drag-and-drop feature enables developers to quickly create GUI-based applications without the need to write extensive codes manually.
- IntelliJ IDEA: IntelliJ IDEA is a Java and Kotlin Integrated Development Environment (IDE) that prioritizes enhancing developer efficiency.
- Oracle JDeveloper: This is a cost-free integrated development environment that streamlines the creation process of Java-based applications, covering all aspects of the application lifecycle.
Infosys Java Developer Interview Questions for Mid-Level Candidates
Here are some of the frequently asked Infosys Java developer job interview questions for candidates with 3 years of experience.
Q16. What does Method Overriding mean?
Answer: Method overriding means having two methods with the same name and parameters (i.e., method signature) but different implementations in parent and child classes. This allows polymorphism as child classes can provide their implementations for the method.
Q17. What class supports string mutable?
Answer: The StringBuilder class in Java supports mutable strings. It allows dynamic modifications to the content of the string. This makes it more efficient for operations that involve frequent modifications to string data compared to the immutable String class.
Q18. Explain the concept of a string immutable.
Answer: String immutable means once a String object is created, its value cannot be changed. Any modifications create a new String object. This makes strings thread-safe as they cannot be modified concurrently.
Q19. Differentiate between String and String Buffer.
Answer: A string is unchangeable, indicating that once a string object is formed, it remains unchanged. However, a StringBuffer can be modified as it is mutable and enables adjustments such as additions, removals, and modifications without the need to create new objects repeatedly.
Q20. Explain the difference between an Array and a List.
Answer: Here are some basic differences between an array and a list:
- Arrays have fixed size, while lists have dynamic size.
- Arrays can store primitive data types, while lists can only store objects.
Q21. What class can you implement using an array?
Answer: The following classes can be implemented using arrays:
- Stack
- Queue
- Heap
Q22. Differentiate between List, Set, and Map.
Answer: In Java, a list is a collection that keeps the order and indexes of its elements. It can have duplicates. On the other hand, Set stores objects in an unordered manner and doesn’t allow for any duplicate entries. Whereas, Map uses key-value pairs to store data and employs hashing as its underlying structure.
Q23. Define the term WeakHashMap.
Answer: WeakHashMap uses weak references for keys, which means if a key is not referenced outside the WeakHashMap, it can be called garbage collected.
Q24. What are the methods in the interface?
Answer: Abstract and public are the default modifiers for interface methods, while public, static, and final are the defaults for interface attributes. Interfaces do not have constructors as they cannot be instantiated to create objects.
Q25. What do you understand by the Serializable interface?
Answer: The Serializable interface is essential for serializing an object. This process involves converting its state into a byte stream so that it can be stored in a database, transmitted through a network, or saved as a file. In reverse, this byte stream allows the recreation of the original Java object when required in memory.
Q26. Explain the terms Static Overloading and Dynamic Overloading.
Answer: Static method overloading enables multiple methods with the same name in a class as long as their parameter lists are different. Dynamic method overloading is an object-oriented programming feature that allows a class to have more than one method with the same name but varying parameters, such as type or number.
Q27. Does Java 8 support multiple interfaces?
Answer: Yes, Java 8 onwards allows implementing multiple interfaces having default methods with the same signatures by overriding them.
Q28. What is the difference between class and interface in Java?
Answer: Classes can hold both variables and methods, which determine the behavior of a specific data type. On the other hand, interfaces act as blueprints that outline a set of related methods without any defined functionality. The actual implementation of these methods is then carried out by the class that implements said interface.
Q29. What does closure mean?
Answer: Closure refers to a self-contained block of code that can be passed as an argument to another function or executed on its own. Essentially, it’s a way of packaging up some behavior (in the form of code) and using it in different parts of a program. In the Java programming language, lambdas are a type of closure.
Q30. Explain the term transient variable.
Answer: Transient variables are a unique type of variable designated with the transient keyword. Unlike other variables, their values are not saved during serialization. Instead, they default to their initial value upon de-serialization.
Infosys Job Interview Questions for Experienced Java Developers
Below are some of the Infosys job interview questions for Java developers with an adequate level of experience
Q31. What’s the difference between an error and an exception?
Answer: The main difference between errors and exceptions is that errors happen during runtime because of problems with the system and cannot be fixed. Whereas exceptions occur due to problems with the application and can be handled and recovered by using try-catch blocks.
Q32. Can you differentiate between HashMap and HashSet?
Answer: One key distinction between HashSet and HashMap is their respective storage of elements. While HashSet only allows for unique elements, with no associated values, HashMap stores data in the form of key-value pairs.
In this structure, keys act as identifiers and are used to retrieve corresponding values from the map. The appropriate choice between these two structures ultimately depends on the specific requirements of a developer’s program.
Q33. What is the life cycle of a thread?
Answer: The process of a thread’s life cycle in Java encompasses the different phases that a thread traverses while being executed. These stages include New, Runnable, Running, Blocked/Waiting, Timed and Terminated states.
Q34. What are the Simple programs in core Java?
Answer: A basic illustration of a core Java program can be seen in the following code:
public class HelloWorld {
public static void main(String[] args) {
System.out.println("
Q35. What is the preprocessor of C called?
Answer: The C preprocessor is called cpp. It processes the source code before compilation by performing the inclusion of header files, macro expansions, etc.
Q36. Can you define an SQL join?
Answer: SQL JOIN allows combining data from two or more tables in a database. It creates a set that can be saved as a table or used as it is. The common types of joins are:
- INNER JOIN: Matches rows from both tables where the condition satisfies.
- LEFT JOIN Fetches all rows from the left table and only matching rows from the right table.
- RIGHT JOIN: Opposite of left join, fetches all rows from the right table and matching rows from the left table.
- FULL JOIN: Fetches rows when there is a match in any one of the tables.
Q37. Explain the different types of inheritance.
Answer: The different types of inheritance in OOP are:
- Single Inheritance: One parent, one child
- Multiple Inheritance: One child, multiple parents
- Multilevel Inheritance: Grandparent, parent, child
- Hierarchical Inheritance: One parent, multiple children
Q38. What are the tokens in C++?
Answer: C++ Tokens are the smallest building blocks of a program. Since C++ is an extension of ‘C’, most elements from ‘C’ can be used in ‘C++’ without any changes to their meaning or function. Therefore, tokens, expressions, and data types remain the same as those found in ‘C’.
Q39. Mention 3 disadvantages of using C++.
Answer: The three disadvantages of C++ are:
- Steep Learning Curve: C++ is a complex language with strict rules and syntax, making it difficult for beginners to learn.
- Memory Management Issues: Since C++ does not have automatic garbage collection, managing memory manually can be challenging and error-prone, leading to potential bugs or crashes in the program.
- Platform-dependent Code: Code written in C++ may not run on different operating systems without modifications due to its platform-specific nature. This makes cross-platform development more time-consuming and complicated compared to other languages like Java or Python.
Q40. What are the differences between heap and stack memory?
Answer: Stack memory is a sort of memory allocation that the OS continuously manages and uses to store local variables in a LIFO order.
On the other hand, heap memory is a type of dynamic memory allocation used for storing objects and data structures that require a longer lifespan than stack memory. Instead of being automatically managed by the OS, heap memory must be explicitly allocated and freed.
Q41. What are the three types of loops in Java?
Answer: Three types of loops in Java are:
- For loop
- While loop
- Do-while loop
For and while loops are examples of entry-controlled loops, meaning that the loop condition is evaluated before each iteration. On the other hand, a do-while loop is an exit-controlled loop where the code block will be executed at least once before evaluating the condition for subsequent iterations.
Q42 What are some differences between Windows and DOS?
Answer: The difference between Windows and DOS is mentioned below.
Feature | Windows | DOS |
Graphical User Interface (GUI) | Windows provides a graphical interface with features like Windows, icons, and a mouse-driven environment, offering a user-friendly experience. | DOS primarily relies on a command-line interface, lacks graphical elements, and requires users to interact through text commands. |
Multitasking | Windows supports multitasking, allowing multiple programs to run simultaneously, with each having its own window and resources. | DOS has limited multitasking capabilities, often requiring users to switch between applications sequentially, and lacks the sophisticated multitasking environment of Windows. |
Memory Management | Windows has advanced memory management, supporting virtual memory, protected mode, and efficient use of system resources. It can handle larger memory sizes and multitasking scenarios. | DOS has limited memory management capabilities, operating in real mode, and facing challenges with memory constraints, especially in handling larger applications and multitasking. |
Q43. Can you mention some advanced-level programming languages?
Answer: Some advanced-level programming languages:
- Java
- C++
- Python
- Ruby
- Perl
- Haskell
- Scala
- R
Q44. List some differences between varchar and char in DBMS.
Answer: The following are the key differences between varchar and char in DBMS:
Feature | VARCHAR | CHAR |
Length Storage | It can store variable-length characters, allowing for efficient storage of varying data lengths. | It stores fixed-length characters, requiring the full allocated space even if fewer characters are stored. |
Space Utilization | It uses only the space required for the stored characters, making it more space-efficient for variable-length data. | It allocates and uses the full designated space, potentially leading to wasted storage for shorter strings. |
Access Speed | Accessing a VARCHAR column is generally slower than accessing a CHAR column due to variable-length storage considerations. | Accessing a CHAR column is faster as it involves fixed-length data, simplifying data retrieval operations. |
Maximum Storage Capacity | It can store up to 8000 characters. | It has a maximum storage capacity of up to 2000 characters. |
Q45. Mention some examples of data structures in C++.
Answer: Some commonly used data structures in C++ are:
- Arrays
- Linked Lists
- Stacks
- Queues
- Trees
- Graphs
- Vectors
- Maps
- Sets
Tips and Tricks to Excel in Infosys Interview Questions for Java Developer
Here are essential tips to enable you to ace your Infosys Java developer interview questions
- Practice Coding Exercise: Practice coding challenges and hands-on problems across different mediums to enhance your knowledge and coding abilities for a Java programmer interview.
- Learn the Core Concept of Java Programming: Refresh your knowledge of fundamental Java programming ideas like data types, declarators, iteration structures, data collections, and principles of object-oriented design.
- Conduct Mock Interview: Before your interview, you can participate in a brief interview section with peers, coworkers, or online tools to simulate an authentic Java technical interview situation.
- Understand the Essentials of Data Structures: When preparing for Infosys interview questions for a Java developer, it is important to enhance your knowledge of vital data organizations and procedural designs utilized in Java development.
Conclusion
To ace your Infosys Java developer interview, you need to understand both core Java concepts and Infosys’ specific requirements. Prepare by familiarizing yourself with the most commonly asked Infosys interview questions for Java developer. These questions primarily focus on crucial technical aspects such as C and C++, OOP concepts, and fundamental programming language knowledge that every developer must be well-versed in. By brushing up on these topics, you can increase your chances of success and confidently take on any challenge that comes your way during the interview. So, gear up, prepare well, and showcase your skills to land your dream job at Infosys!
Did you find this blog helpful to prepare for the interview? Let us know in the comment section below. Also, consider exploring these top 17 Problem-Solving interview questions and answers to adequately equip yourself for your upcoming interview.
FAQs
Answer: To excel in a Java Developer interview, it is important to have a solid understanding of OOP principles, Java frameworks, design patterns, algorithms, and data structures. Practicing coding questions and honing problem-solving skills can also boost confidence and performance during the interview.
Answer: The level of difficulty is moderate. With strong technical and communication abilities, you can successfully navigate through all stages without encountering significant obstacles.
Answer: Infosys conducts a three-round interview process for placements. The first round is an online assessment test which is followed by a technical interview, and finally an HR interview.
Answer: Typically, the hiring process at Infosys takes around 13.89 days on average. However, the waiting time for an interview can range from two weeks to several months, depending on how well your profile matches with the available projects. If you have already interviewed and are waiting for the final decision, you can expect to hear from Infosys within two weeks.
Answer: To work at Infosys, you should be proficient in diverse technologies such as Windows and Linux operating systems, virtualization, and network infrastructure. Knowing programming languages like Python and SQL, and having hands-on experience on cloud-based platforms like AWS and Azure can also be advantageous.