Tech Mahindra Senior Java Software Engineer Interview Questions and Answers

Q1. What is java and how it is platform independent
Ans. 
Java is a high-level programming language used to develop applications that can run on any platform.
• Java code is compiled into bytecode that can run on any platform with a Java Virtual Machine (JVM)

• JVM acts as an interpreter and translates bytecode into machine code

• Java's platform independence is achieved through the 'Write Once, Run Anywhere' (WORA) principle

• Java's standard library provides platform-independent APIs f
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Q2. What are new features in Java 8
Ans. 
Java 8 introduced several new features including lambda expressions, streams, and default methods.
• Lambda expressions for functional programming

• Streams for efficient processing of large data sets

• Default methods for backward compatibility

• Date and Time API for improved handling of date and time

• Nashorn JavaScript engine for improved performance

• Type annotations for improved type checking

• Parallel array sorting for improved p...read more
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Q3. What is serialization in java
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Serialization is the process of converting an object into a stream of bytes to store or transmit it.
• Serialization is used to save and restore object states

• Java provides Serializable interface to implement serialization

• Serialization can be used for inter-process communication and distributed systems

• Deserialization is the process of converting a stream of bytes back into an object

• Serialization can be customized using rea
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Q4. What is static variable
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Static variable is a variable that belongs to the class and not to the instance of the class.
• Static variables are declared using the 'static' keyword.

• They are initialized only once, at the start of the program.

• They can be accessed using the class name, without creating an instance of the class.

• Changes made to a static variable are reflected across all instances of the class.

• Example: 'public static int count = 0;'
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Q1. What is collections and why to use them in java
Ans. 
Collections are a group of classes and interfaces used to store and manipulate groups of objects in Java.
• Collections provide a way to store and manipulate groups of objects in Java

• They offer various data structures like List, Set, Map, etc.

• Collections provide methods to add, remove, and search for elements in the data structures

• They also offer algorithms for sorting and searching elements

• Examples include ArrayList, Has
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Q2. What is ResultSet in Java and why we should avoid it
Ans. 
ResultSet is an interface in Java used to retrieve data from a database. It should be avoided due to its performance issues.
• ResultSet is used to retrieve data from a database in Java

• It has performance issues and should be avoided if possible

• Alternative options like JPA or Hibernate can be used instead
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Q1. Why you want to join Infosys
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Q2. Tell me something about infosys
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Q1. What are intermediate and terminal operations
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Q2. Predefined functional interface
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Q3. Ways to create Thread
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Q1. Internal working of HashMap
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Q2. Features of java8
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Q3. Use of synchronized keyword
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Q4. Difference between failsafe and fail fast and also its implementation
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Q5. Coding question : sort an array, use of streams to find names from employee object whose salary is greater than 50000
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Q6. Difference between concurrent and generic collection
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Q7. What is string pool. What is string literal?
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Q8. Security measures used in your project
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Q9. What is difference between rest and soap
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Q10. What do u mean by REST state
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Q11. What is serialization? What is the way to stop serialization?
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Q1. Difference between failsafe and faifast
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Q2. Difference between concurrent and generic collection
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Q3. Security measures used in current project
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Q4. Why you are leaving your current organization and follow up questions on that
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Q1. Java 8 , java 11 and java 17 features?
Ans. 
Java 8 introduced lambda expressions, Java 11 added local-variable syntax for lambda parameters, and Java 17 included sealed classes and pattern matching.
• Java 8 introduced lambda expressions for functional programming.

• Java 11 added local-variable syntax for lambda parameters to simplify code.

• Java 17 included sealed classes to restrict inheritance and pattern matching for instanceof checks and type casts.
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Q2. Dispatcher servlet, design patterns
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Q3. @SpringbootApplication annotation, actuators
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Q4. String Coding question with java 8 features such as lambda function and stream api
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Q5. Number of words in a string
Ans. 
Count the number of words in a given string.
• Split the string by spaces and count the number of resulting elements.

• Handle edge cases like multiple spaces or empty strings.

• Consider punctuation marks as part of words unless specified otherwise.
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Q6. Microservice design patterns
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It's walkin, so they conducted 1 technical mcqs round.

Q1. Multi threading
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Q2. Internal working of hashmap
Ans. 
HashMap in Java is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values based on keys.
• HashMap uses an array of buckets to store key-value pairs.

• Keys are hashed to determine the index in the array where the key-value pair will be stored.

• In case of hash collisions, a linked list or a balanced tree is used to store multiple key-value pairs in the same bucket.

• HashMap allows null keys...read more
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Q3. Spring batch related
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Q4. Non repeating characters in a array
Ans. 
Function to find and return all non-repeating characters in an array of strings.
• Iterate through the array and count the occurrences of each character using a HashMap.

• Then iterate through the array again and check if the count of each character is 1, if so add it to the result list.

• Return the list of non-repeating characters.
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Q5. 3rd highest salary
Ans. 
To find the 3rd highest salary in a database, we can use a SQL query with the 'LIMIT' and 'OFFSET' keywords.
• Use a SQL query with 'ORDER BY salary DESC' to sort the salaries in descending order.

• Use 'LIMIT 1 OFFSET 2' to skip the first two highest salaries and retrieve the third highest salary.

• Example: SELECT salary FROM employees ORDER BY salary DESC LIMIT 1 OFFSET 2;
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Q6. Qualifier vs primary
Ans. 
A qualifier in Java is used to specify additional information about a primary, which is the main data type or variable.
• A primary in Java is the main data type or variable, while a qualifier provides additional information about the primary.

• Qualifiers can be used to modify the behavior or characteristics of a primary.

• For example, in Java, 'final' is a qualifier that can be used to make a variable constant.
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Q7. Controller vs restcontroller
Ans. 
The main difference is that @RestController is a specialized version of @Controller that is used for RESTful web services.
• Both @Controller and @RestController are used in Spring MVC to handle HTTP requests, but @RestController is specifically used for RESTful web services.

• @Controller is used to create web pages, while @RestController is used to return data in JSON or XML format.

• @RestController is a convenience annotati...read more
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Q8. Spring boot annotataions
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Q9. Oops concepts with examples
Ans. 
OOP concepts include inheritance, encapsulation, polymorphism, and abstraction.
• Inheritance: Allows a class to inherit properties and behavior from another class. Example: class Dog extends Animal.

• Encapsulation: Bundling data and methods that operate on the data into a single unit. Example: private variables with public getter and setter methods.

• Polymorphism: Ability for objects to be treated as instances of their paren...read more
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Q10. Spring batch configuration
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Q11. They covered all java, spring and Microservices
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Q1. Microservices architecture
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Q2. How do Microservices communicate
Ans. 
Microservices communicate with each other through various communication protocols like HTTP, messaging queues, and gRPC.
• Microservices can communicate over HTTP using RESTful APIs.

• Messaging queues like RabbitMQ or Kafka can be used for asynchronous communication between microservices.

• gRPC is a high-performance, open-source RPC framework that can be used for communication between microservices.

• Service discovery mechanism...read more
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Q3. How to access the Microservice end point
Ans. 
Microservice endpoints can be accessed using HTTP requests with the appropriate URL
• Use HTTP methods like GET, POST, PUT, DELETE to interact with the microservice

• Construct the URL with the base URL of the microservice and the specific endpoint path

• Include any necessary headers or parameters in the request for authentication or data filtering
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Q4. Why we use microservices
Ans. 
Microservices allow for modular, scalable, and flexible software development by breaking down applications into smaller, independent services.
• Microservices enable easier maintenance and updates as each service can be developed, deployed, and scaled independently.

• They improve fault isolation, as failures in one service do not necessarily affect the entire application.

• Microservices promote agility and faster time-to-mark...read more
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Q1. Given an array {1, 2, 1, 4, 5, 4, 8, 7}, how can you use Streams to remove duplicates while retaining only the even numbers?
Ans. 
Use Streams to remove duplicates and retain only even numbers from an array.
• Convert the array to a stream using Arrays.stream()

• Use distinct() to remove duplicates

• Filter out odd numbers using filter()

• Collect the result using collect(Collectors.toList())
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Q2. What is the use of Static and final when you will use Static methods
Ans. 
Static methods can be accessed without creating an instance of the class, while final keyword makes the method unchangeable.
• Static methods belong to the class itself, not to any specific instance

• Final keyword ensures that the method cannot be overridden in subclasses

• Static methods are commonly used for utility methods that do not require access to instance variables

• Example: Math class in Java has static methods like Ma
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Q3. What is the difference between @restController and @controller Annotation
Ans. 
The @RestController annotation is used to define RESTful web services while @Controller annotation is used to define MVC controller.
• RestController is a specialized version of Controller used for RESTful web services

• RestController eliminates the need for @ResponseBody annotation

• Controller is used for traditional MVC controller functionality

• RestController returns data directly without needing to go through a view resolve...read more
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Q4. What is microservices why we use it
Ans. 
Microservices are a software development technique where applications are composed of small, independent services that communicate with each other.
• Microservices allow for easier scalability and maintenance of complex applications.

• Each service in a microservices architecture can be developed, deployed, and scaled independently.

• Microservices promote flexibility and agility in software development.

• Examples of companies us...read more
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The first round was an interview conducted with a GENAI virtual bot.

Q1. Internal architecture of Spring boot, how enable autoconfiguration works
Ans. 
Spring Boot uses autoconfiguration to automatically configure the Spring application based on dependencies and properties.
• Spring Boot autoconfiguration is achieved through @EnableAutoConfiguration annotation

• Autoconfiguration classes are located in the org.springframework.boot.autoconfigure package

• Autoconfiguration classes are conditionally applied based on the presence of specific classes or properties
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Q2. Questions mostly on microservices and coding question on restTemplate
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Q1. Difference between hashmap and hash table
Ans. 
HashMap is non-synchronized and allows null values, while HashTable is synchronized and does not allow null values.
• HashMap is non-synchronized, meaning it is not thread-safe, while HashTable is synchronized and thread-safe.

• HashMap allows null values for both keys and values, while HashTable does not allow null keys or values.

• HashMap is generally preferred for non-thread-safe applications, while HashTable is used in mul
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Q2. Static block related questions
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Q3. Arraylist and linkedlist question
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