IBM Consulting Junior Java Developer Interview Questions and Answers

It's walkin, so they conducted 1 technical mcqs round.

Q1. Multi threading
Add your answer
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
Answered by AI
Add your answer
Q3. Spring batch related
Add your answer
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.
Answered by AI
Add your answer
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;
Answered by AI
Add your answer
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.
Answered by AI
Add your answer
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
Answered by AI
Add your answer
Q8. Spring boot annotataions
Add your answer
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
Answered by AI
Add your answer
Q10. Spring batch configuration
Add your answer
Q11. They covered all java, spring and Microservices
Add your answer

Q1. Microservices architecture
Add your answer
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
Answered by AI
Add your answer
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
Answered by AI
Add your answer
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
Answered by AI
Add your answer

Q1. Explain architecture of your project
Add your answer
Q2. Some questions on Java, Spring Boot and sql
Add your answer

Q1. Project flow and some behavioural questions
Add your answer
Q2. Project contribution of yours
Ans. 
Developed a web application for tracking employee attendance and performance
• Implemented user authentication and authorization using Spring Security

• Utilized Hibernate for database interaction and data persistence

• Designed and developed RESTful APIs for frontend integration

• Used AngularJS for frontend development to create interactive user interfaces
Answered by AI
Add your answer

Q1. Basic formalities before offer release
Add your answer

Q1. What are the design patterns you know in java
Ans. 
Design patterns in Java are reusable solutions to common problems in software design.
• Creational patterns (e.g. Singleton, Factory, Builder)

• Structural patterns (e.g. Adapter, Decorator, Facade)

• Behavioral patterns (e.g. Observer, Strategy, Template Method)
Answered by AI
Add your answer
Q2. What is daimond problem
Ans. 
The diamond problem occurs in multiple inheritance when a class inherits from two classes that have a common ancestor, leading to ambiguity in method invocation.
• Diamond problem arises in multiple inheritance when a class inherits from two classes that have a common ancestor.

• It leads to ambiguity in method invocation as the compiler cannot determine which inherited method to invoke.

• Example: Class A has a method 'display...read more
Answered by AI
Add your answer

Q1. What is Executer Service?
Ans. 
ExecutorService is an interface in Java that provides a way to manage and control the execution of threads in a multithreaded environment.
• It is part of the java.util.concurrent package.

• It provides methods to submit tasks for execution, manage thread pools, and control the execution of tasks.

• It allows for the execution of tasks asynchronously and provides features like scheduling, cancellation, and monitoring of tasks.

• E...read more
Answered by AI
Add your answer
Q2. What is the use of JPA?
Ans. 
JPA is a Java specification for mapping Java objects to relational databases.
• JPA stands for Java Persistence API

• It provides a way to map Java objects to database tables and vice versa

• JPA simplifies the development of data access layer in Java applications

• It supports object-relational mapping (ORM) and allows developers to work with entities, relationships, and queries in a more object-oriented way
Answered by AI
Add your answer
Q3. Explain about PreparedStatement
Ans. 
PreparedStatement is used in Java to execute parameterized SQL queries to prevent SQL injection attacks.
• PreparedStatement is a subinterface of Statement in Java.

• It is used to execute parameterized SQL queries.

• It helps prevent SQL injection attacks by automatically escaping special characters.

• Example: PreparedStatement pstmt = connection.prepareStatement("SELECT * FROM users WHERE username = ?");
Answered by AI
Add your answer
Q4. Program to find the missing numbers from Array
Ans. 
Program to find missing numbers from Array
• Iterate through the array and store each number in a HashSet

• Then iterate from 1 to the length of the array and check if each number exists in the HashSet

• If a number is not found in the HashSet, it is a missing number
Answered by AI
Add your answer

Q1. Comparable vs Comparator
Ans. 
Comparable is an interface used for natural ordering, while Comparator is used for custom ordering in Java.
• Comparable interface is used to define the natural ordering of objects. It is implemented by the class whose objects are to be sorted.

• Comparator interface is used to define custom ordering of objects. It is implemented by a separate class that compares objects based on specific criteria.

• Example: Sorting a list of ...read more
Answered by AI
Add your answer
Q2. Difference between List and Set

Ans. 

List allows duplicate elements and maintains insertion order, while Set does not allow duplicates and does not maintain order.

• List can contain duplicate elements, Set cannot

• List maintains insertion order, Set does not guarantee order

• List is implemented by classes like ArrayList, LinkedList, Set is implemented by classes like HashSet, TreeSet

• Example: List list = new ArrayList<>(); Set set = new HashSet<>();

Add your answer