Mastercard

Java Language Fundamentals

• Can we extend string class?

• Why string class is immutable?

• What is the difference between String = "s" and new String("s")

• Are strings eligible for garbage collection

• Explain the deep explanation of equals/hashcode method.

• What are immutable objects

• Java Call by value or call by reference? Demonstrate using an example.

• What is generics in Java

• Class vs object

• How to create a class as static

• What happens when return is used inside a try block

• What happens when System.exit() is used inside a try block

• What is the difference between path and classpath

• Can a constructor be made final?

• What is the finalize method?

• Explain the Stream API in Java 8.

• Explain interfaces in the collection framework.

Threads and Concurrency

• How to return a value from a thread?
• What is the Callable interface?
• How can we create a thread in Java?

• Explain Daemon threads.
• Explain race condition.
• How locks are used in multithreading?
• How synchronization is implemented in Java?
• On which object the lock is implemented when we use a synchronized method?
• In which case do we not need to pass any mutex object?

Collections

• HashMap internals

• Concurrent HashMap vs HashMap

• Benefits of Optional class

• Java 8/9 features - Questions around Optional class, Stream API

• What are the methods provided by HashMap

• How to handle custom objects as key in HashMap
• If equals returns true and hashcode method returns false in HashMap, will it add the object

• Explain Queue data structure.

• Explain Tree data structure.
• What problems are related to tree data structures?

Design Patterns

• Java design patterns - Explain at least 1 or 2 patterns from each category

• Demonstrate the builder pattern

• Demonstrate the observer pattern / strategy pattern

• Factory Design Pattern

• Builder Design Pattern

• Which design patterns have you used in your project

Exceptions and Errors

• Can we catch the error?

• Can have custom exceptions? Can we have custom errors?

Coding

• Find odd numbers from list of integers using Stream API

• Write a method to identify vowels in a string and number of times vowels are repeated in the same string

• Return true if a list of numbers contains odd numbers, false otherwise using Java 8
• Describe your role in your current project

• How to review code of your team members and which rules you keep in mind

• Explain how to find the kth smallest element in an organization, where k represents the third youngest student.

Spring Boot

• How to establish connection to DB in Spring Boot?

• Can we do autowiring by interface?

• In case of autowiring by interface, what if there are two different implementations? Which bean will be autowired?

• How to change the default web server in Spring Boot

• How to retry in Spring Boot

• How to do a health check

• What is the difference between @Component, @Service, and @Autowire annotations

• What is JPA

• Have you used Hibernate JPA in your Spring Boot application and how

• What is the difference between SpringRunner and Mockito

• What is the difference between soap and REST API

• What is the difference between JSON and XML

• What is @RequestBody and @ResponseBody annotation
• What is @RequestMapping annotation

• What is Spring Actuator

• What are the REST API URL patterns

• Create a REST controller class and add all HTTP methods

• Explain @Primary annotation.

• How to resolve circular dependency problem?
• When to use @SpringBootApplication and @EnableAutoConfiguration annotations?

Microservices

• Can we establish parallel connections to separate DB in Java?

• Exception handling in microservices

• Circuit breaker pattern

• Data consistency in microservices in case of failure

• How to scale a pod in case of load (e.g. 70%)

• Benefits of microservices architecture? How is it different from monolithic application?

• How to do health check of microservices

• How to retry if a service is down

• How do circuit breakers work

Testing

• Different types of testing used in a project

• How to mock objects in unit tests?

• Questions around the Mockito library

• What is a contract test / functional test / integration test, etc.

• Explain the CI/CD process

Miscellaneous

• What is Sonar and what is its use

• Give a rating score of your skills