XUS_IN_Java

Java

Key Skills

Java developer with a firm knowledge in object-oriented design and software development. Experience in building distributed, service oriented, micro-service-style and cloud-based solutions using Java Spring boot.

• Must have 5+ years of experience in Enterprise Java 8 and above.
• Strong in Core Java (Collections, Threads, Regular Expressions, concurrency, Lambdas, Reactive, Exception handling).
• Strong experience in microservices and event driven processing systems.
• Experience with architecting and implementing apps using Spring Boot, Spring Cloud including Spring MVC, Spring Boot, Spring JDBC, and Spring Cloud.
• Good knowledge on Relational database (Oracle / MySQL / Postgres) or NOSQL database is preferred.
• Mandatory knowledge of Cloud AWS/GCP Services.
• Experience in writing & automating test scripts using Mockito/JUnit, SpringbootTest etc.
• Must have experience working with concepts like Domain Driven Design, Microservices, Reactive Architecture etc.
• Must be capable of doing code reviews and mentor the junior developers to drive towards high quality deliverables.
• Strong background culture of delivering projects with first time right / Zero defects in Production.
• Very good analytical, problem solving ability, verbal, and written communication skills.

Screening  Questions  

What is a functional interface in Java 8. ? Example of Functional interface in java  

Answer : 

A functional interface is an interface with a single abstract method, such as Runnable, Callable, Comparator 

Can we create custom Functional Interface ? 

Answer : yes 

What are Streams API ?   

Answer :  Streams allow you to process collections in a functional style, with operations like map, filter, reduce, and collect. 

What are default methods in interfaces, and why were they introduced in Java 8? 

Answer:  

Default methods allow interfaces to have methods with implementations. They were introduced to support backward compatibility so that interfaces could be updated without breaking existing implementations. 

What is Method Overloading and Method overriding ? is it determined at runtime or compile time  

Answer:  

Method overloading  

• Allows a class to have more than one method with the same name, but with different parameter lists (different type, number, or both of parameters).  

• Methods can be overloaded in the same class or in a subclass.  

• Overloading is determined at compile time  

Method Overriding  

• Method overriding occurs when a subclass provides a specific implementation for a method that is already defined in its superclass.  

• The method in the subclass must have the same name, return type, and parameter list as the method in the superclass.  

• Overriding is determined at runtime 

Which collection would you choose when you need to maintain unique elements but also need to maintain order  

Answer:  Linked Hashset 

What is Executor Service in java 

Manages a pool of threads to execute tasks asynchronously and supports task scheduling and thread pool management. 

What are Spring boot profiles  

Aswer :  Spring Boot profiles allow you to segregate parts of your application configuration and make it available only in certain environments (e.g., development, testing, production). 

How do you handle exceptions in a Spring Boot application, both global and controller-specific exception handling? 

Answer: 

In Spring Boot, exceptions can be handled at the controller level using @ExceptionHandler and globally using @ControllerAdvice. 

How do Microservices Communicate with each other  

Microservices typically communicate via APIs using protocols like HTTP/REST, gRPC, or message brokers for asynchronous communication (e.g., RabbitMQ, Kafka). 

What is the role of an API Gateway in a microservices architecture. 

An API Gateway acts as a single entry point for clients, routing requests to appropriate microservices, handling load balancing, security, request transformation, and response aggregation. 

L1 Interview  

1. Evaluate Java concepts like inheritance, polymorphism, exception handling, collections and algorithms (35 min) 

1. Provide code snippets asking for program outputs checking the above concepts 

1. Ask to write program testing collections , multithreading  

1. List the words in order of number of times they are repeated in the list if repeat count is same use alphabetical order  

["apple", "banana", "apple", "orange", "banana", "apple", "grape", "orange", "banana", "grape"] 

Output : apple banana grape orange 

1. Split a large product list into sublist in (chunks of 10 ) . Sequence of the sublist should be maintained .  Ask for approach, look for multithreaded approach 

Output  

chunk 1: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]  

Chunk 2: [11, 12, 13, 14, 15, 16, 17, 18, 19, 20]  

Chunk 3: [21, 22, 23, 24, 25, 26, 27, 28, 29, 30] 

 Chunk 4: [31, 32, 33, 34, 35, 36, 37, 38, 39, 40]  

Chunk 5: [41, 42, 43, 44, 45, 46, 47, 48, 49, 50] Chunk 6: [51, 52, 53, 54, 55] 

1. Medium level coding problem 

1. Java 8 Features ( 

1. Ask to write a program that test concepts like lambda, streams , method references, Functional interface  

1. e.g. Given a list of Employee objects, write a program to return a map with key as city and the value as employee above 40 years with highest salary 

1. Database -  Relational Query / ORM – JPA mapping  

(20 min)  

1. Unit testing  -  code snippet and ask to write JUNIT test . Check how they mock DB object, Ask how they cover code coverage in their project  

1. Spring boot -   Question on Spring boot components , Async Method calling ,JDBC Template , Spring Data  

1. Spring Cloud  concepts  

L2  

1. 1-2 Generic coding exercise . look for problem solving approach , code optimization (15 min) e.g.                  

1.  finding the longest substring without repeating characters 

1. Given a string containing  expression '(', ')', '{', '}', '[' and ']', determine if the input expression  is valid. i.e opening braces are correctly closed 

1. Longest Palindromic Substring 

1. Given an array of integers and a target sum, write a program to find all unique pairs of integers in the array whose sum equals the target sum. 

Nested loop approach resulting in O(n^2) complexity 

1. Ask to write Spring Boot Skeleton for basic steps and annotations (15 min) 

1. Include starter dependency  

1. Use of auto configure ,auto wire for service,Repository, Entity object  

1. If db credential in application properties file , followup if this is best practice  

1. Ask about JDBC Template, Spring Data 

1. Consume external API using Rest Template  

1. Approach if need to consume from Multiple APIs , Multithreaded Approach 

1. Exception handling  

1. Caching startegies 

(15 min) 

1. How they implement Fault Tolerance -  retry pattern , Circuit breaker pattern  

1. Current project Architecture , Ask about event driven flow , is it on cloud/ on prem what message broker they using . how service discovery and communication between services was done 

1. How they debug an issue in Distributed environment, Logging , Tracing . what technology they use 

1. How they do Service Discovery  

1. What they do for security Oauth, JWT  

1. Distributed Transaction strategies (are they use any framework like Apache Camel,Axon , Spring Cloud Data Flow, Spring Cloud Stream) 

1. Saga pattern  

1. Choreography – compensating transaction 

1. Orchestration –  
2. Handling Idempotency