Jforce Solutions Java Developer Interview Questions and Answers for Experienced

Q1. Method reference vs lambda functions
Ans. 
Method reference is a shorthand syntax for lambda expressions in Java.
• Method reference is more concise and readable than lambda expressions.

• Method reference can be used to refer to static methods, instance methods, and constructors.

• Lambda expressions are more flexible and can be used in situations where method reference is not applicable.
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Q2. SOLID Principles
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Q1. Oops concept and collections
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Q2. MySql and springBoot
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Q1. Regular core java, OOPS, Spring Boot questions. It was like a rapid-fire round.
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Q1. Coding question - find repeat elements in an array
Ans. 
Find repeat elements in an array of strings
• Iterate through the array and store each element in a HashMap with its count

• Check if the count of any element is greater than 1, then it is a repeat element

• Return the repeat elements found in the array
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Q2. Project related questions
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Q3. Build a basic CRUD REST API endpoint
Ans. 
Build a basic CRUD REST API endpoint
• Create a REST API endpoint for each CRUD operation (Create, Read, Update, Delete)

• Use HTTP methods like POST, GET, PUT, DELETE to perform CRUD operations

• Implement data validation and error handling for each operation

• Utilize a framework like Spring Boot or Express.js to simplify API development
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Q1. Behavioral questions
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Q2. Technical questions about SpringBoot and microservices
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Q3. SQL question - third highest salary
Ans. 
To find the third highest salary in a SQL table, you can use the 'SELECT TOP 1' statement with 'ORDER BY salary DESC OFFSET 2 ROWS FETCH NEXT 1 ROWS ONLY'.
• Use the 'SELECT TOP 1' statement to retrieve only one record

• Order the records by salary in descending order using 'ORDER BY salary DESC'

• Skip the first two highest salaries using 'OFFSET 2 ROWS'

• Fetch the next record after skipping the first two using 'FETCH NEXT 1 ROW
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Q1. Java streams related questions
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Q1. What is wait, notify, notifyall
Ans. 
wait, notify, and notifyAll are methods used for inter-thread communication in Java.
• wait() method causes the current thread to wait until another thread invokes the notify() or notifyAll() method for this object.

• notify() method wakes up a single thread that is waiting on this object's monitor.

• notifyAll() method wakes up all threads that are waiting on this object's monitor.
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Q2. Difference between spring and springboot
Ans. 
Spring is a framework for building Java applications, while Spring Boot is a tool that simplifies the setup and configuration of Spring applications.
• Spring is a comprehensive framework for building Java applications, providing support for various modules like Spring MVC, Spring Security, and Spring Data.

• Spring Boot is an opinionated tool that simplifies the setup and configuration of Spring applications by providing de...read more
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Q3. What is lambda expression
Ans. 
Lambda expression is a concise way to represent an anonymous function in Java.
• Lambda expressions are used to provide implementation of functional interfaces.

• They enable you to treat functionality as a method argument, or code as data.

• Syntax: (parameters) -> expression or (parameters) -> { statements; }

• Example: (int a, int b) -> a + b
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Online assessment MCQs with 3 questions where we nmed to find bug in existing logic

Q1. What are new features in Java 8 explain in brief
Ans. 
Java 8 introduced new features like lambda expressions, functional interfaces, streams, and default methods.
• Lambda expressions allow you to write code in a more concise and readable way.

• Functional interfaces provide a single abstract method for functional programming.

• Streams enable processing sequences of elements in a functional style.

• Default methods allow interfaces to have method implementations.

• Example: Lambda expr...read more
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Q1. Introduction and expectations
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Q1. Basic java questions
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Q1. Oops concepts in details
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Object-oriented programming concepts in Java
• Encapsulation: bundling data and methods together

• Inheritance: creating new classes from existing ones

• Polymorphism: using a single interface to represent multiple types

• Abstraction: hiding implementation details

• Encapsulation: grouping related data and methods into a class

• Association: relationship between two or more objects

• Composition: creating complex objects by combining simp...read more
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Q2. Method overloading and overriding
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