MasterCard Principal Java Developer Interview Questions and Answers

Q1. Code singleton design pattern in java
Ans. 
Singleton design pattern ensures a class has only one instance and provides a global point of access to it.
• Create a private static instance of the class

• Provide a public static method to access the instance

• Ensure the constructor is private to prevent instantiation of multiple objects
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Q2. 2 sum in java
Ans. 
2 sum problem in Java involves finding two numbers in an array that add up to a specific target value.
• Use a HashMap to store the difference between the target value and each element in the array.

• Iterate through the array and check if the current element's complement exists in the HashMap.

• Return the indices of the two numbers that add up to the target value.
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Q3. How to make a class immutable
Ans. 
To make a class immutable, ensure that its state cannot be changed after instantiation.
• Make all fields private and final

• Do not provide setter methods

• Ensure that any mutable objects within the class are also made immutable
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Q4. Async annotation
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Q5. Spring-starter dependencies
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Q1. What is cyclomacic complexity
Ans. 
Cyclomatic complexity is a software metric used to measure the complexity of a program.
• It measures the number of linearly independent paths through a program's source code.

• It helps in identifying complex code that may be difficult to maintain or test.

• A higher cyclomatic complexity indicates a higher risk of errors and bugs in the code.

• It is calculated using the formula: E - N + 2P, where E is the number of edges, N is ...read more
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Q2. Simple output questions based on inheritance
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Q3. OWASP top 10 security vulnerabilities
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Writing URLShortener or LoadBalancer in Java

Q1. ACID definition and Isolation levels
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Q2. CAP Theoreme and Distributed transactions
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Q1. Design patterns
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Q2. How hashcode and equals related to each other
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Q1. HLD for rental property website
Ans. 
High-level design for a rental property website
• Use case analysis to identify key functionalities such as property listing, search, booking, payment

• Design a user-friendly interface with filters, maps, and photos for property listings

• Implement a secure payment gateway for online transactions

• Utilize a database to store property details, user information, and booking history
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CodeSignal platform 2 easy and 2 difficult questions

A coding Test of 100 Minutes was scheduled on the HackerRank platform.
6 MCQs related to the backend.
1 Coding Question
1 Backend Spring Boot Coding question

Q1. Screening Round
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Q2. Question Related to Resume
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Q1. Experience in ReactJS
Ans. 
I have 2 years of experience in ReactJS, including building interactive user interfaces and integrating with backend services.
• Developed a responsive web application using ReactJS, Redux, and Material-UI

• Implemented RESTful APIs to fetch and update data in the application

• Utilized React Router for client-side routing and navigation

• Worked on optimizing performance by using memoization and lazy loading techniques
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Q2. Experience in Spring Boot
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