91social Java Developer Interview Questions and Answers

A standard online test conducted through one of the testing platforms.

Q1. Java 8 features
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Q2. Rest API
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Q3. Java 8 coding problem
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Q4. Collections
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Q1. It was based on my previous project
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Q1. Explain Spring Boot
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Q2. What is Redux in React
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Q3. What is Context API in React
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Q1. Difference between Hashset and Treeset
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Q2. Final Finally and finalize difference
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Q1. Tell me about your project
Ans. 
Developed a web-based inventory management system for a retail company.
• Used Java, Spring Boot, and MySQL for backend development.

• Implemented user authentication and authorization using Spring Security.

• Designed a responsive front-end using HTML, CSS, and JavaScript.

• Integrated barcode scanning functionality for efficient inventory tracking.
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Q2. Class vs object
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A class is a blueprint or template for creating objects, while an object is an instance of a class.
• A class defines the properties and behaviors of objects, while an object is a specific instance of a class.

• Classes can be used to create multiple objects with similar characteristics.

• Objects have state (attributes) and behavior (methods) defined by the class.

• Example: Class 'Car' defines properties like 'color' and 'model'...read more
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Q1. Salary expectation
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Q2. Date to join?
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Q1. Basics of java like string ,string builder ,Buffer,scp
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Q2. Spring boot annotaions
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Q1. Diff between abstract class and interface
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Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.
• Abstract class can have constructor, fields, and methods, while interface cannot have any of these.

• A class can extend only one abstract class, but can implement multiple interfaces.

• Abstract classes are used to define a common behavior among subclasses, while interfaces are used to define a contract for classes...read more
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Q2. Explain about handler methods
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Handler methods in Java are methods that are responsible for handling incoming requests and generating responses.
• Handler methods are typically defined in classes annotated with @Controller or @RestController.

• These methods are mapped to specific URLs using @RequestMapping or other mapping annotations.

• Handler methods can have parameters such as HttpServletRequest, HttpServletResponse, or model attributes.

• The return value...read more
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Q1. Prime number program
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A program to check if a given number is prime or not.
• Create a function to check if a number is prime by iterating from 2 to the square root of the number.

• If the number is divisible by any number other than 1 and itself, it is not prime.

• Handle edge cases like 0, 1, and negative numbers separately.
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Q2. 3rd highest salary employee
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To find the 3rd highest salary employee, we can use a SQL query with the 'LIMIT' and 'OFFSET' keywords.
• Use a SQL query to select distinct salaries in descending order

• Use 'LIMIT 1 OFFSET 2' to get the 3rd highest salary

• Join this result with the employee table to get the employee details
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Q1. Basic java and API
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Q1. Normal Question
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