Luxoft Senior Java Developer Interview Questions and Answers

Q1. How annotation works?
Ans. 
Annotations in Java provide metadata about a program that can be used by the compiler or at runtime.
• Annotations start with the @ symbol.

• Annotations can be used to provide information to the compiler or to runtime environments.

• Annotations can be used to define custom metadata for classes, methods, fields, etc.

• Annotations can also be used for code generation, documentation, and validation.

• Examples of annotations in Java ...read more
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Q2. CondurentSkipListMap, how does it work
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ConcurrentSkipListMap is a concurrent, sorted map implementation in Java.
• ConcurrentSkipListMap is a concurrent version of SkipListMap, which is a sorted map implementation based on skip list data structure.

• It allows multiple threads to access and modify the map concurrently.

• It provides logarithmic time complexity for most operations, making it efficient for concurrent access.

• Example: ConcurrentSkipListMap<Integer, S...read more
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2 Basic Programsl on LRU amd strings

Q1. Core java , java 8 concepts, spring core concepts
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Q1. Salary discussion
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Q1. Policy briefing
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Q1. Coding question - Find out max repeated number from given string
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Find the maximum repeated number in a given string by counting occurrences of each digit and identifying the highest one.
• Iterate through the string: Loop through each character in the string to check if it's a digit.

• Count occurrences: Use a map or array to count how many times each digit appears.

• Identify the maximum: After counting, determine which digit has the highest count.

• Return the result: Output the digit that is...read more
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Q2. What are the disadvantages of indexing?
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Indexing can improve query performance but has drawbacks like increased storage and maintenance overhead.
• Increased storage requirements: Indexes consume additional disk space. For example, a large table with multiple indexes can significantly increase storage needs.

• Slower write operations: Inserting, updating, or deleting records can be slower due to the need to update indexes. For instance, adding a new row requires u...read more
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Q1. Principal of garbage collection
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Garbage collection is an automatic memory management process that frees up memory occupied by objects that are no longer in use.
• Garbage collection is performed by the JVM.

• It helps prevent memory leaks and improves application performance.

• There are different types of garbage collectors such as serial, parallel, CMS, and G1.

• Garbage collection can cause pauses in the application, which can be minimized by tuning the JVM p...read more
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Q2. Micro services design pattern
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Microservices design pattern is an architectural approach to building software applications as a collection of small, independent services.
• Microservices are independently deployable and scalable

• Each microservice focuses on a specific business capability

• Communication between microservices is done through APIs

• Microservices can be developed using different programming languages and technologies

• Examples of companies using ...read more
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Q3. Spring bòot annotations
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Q4. Sessions in hibernate
Ans. 
Sessions in Hibernate are used to manage the interaction between the application and the database.
• A session is a single-threaded object that represents a connection between the application and the database.

• It is responsible for managing the persistence of objects, executing queries, and providing transactional support.

• A session can be obtained from a session factory and should be closed when no longer needed.

• Example: S...read more
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Q5. What is Hash collusion
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Hash collusion is when two different inputs produce the same hash value.
• It is a security vulnerability in hash functions.

• Attackers can exploit this vulnerability to create a collision attack.

• For example, an attacker can create a malicious file with the same hash value as a legitimate file to bypass security checks.
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Q6. What is saga design pattern
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Saga design pattern is used to manage long-lived transactions between microservices.
• It ensures that all services involved in a transaction are either committed or rolled back together.

• It uses a sequence of local transactions to achieve global consistency.

• It can be implemented using either choreography or orchestration.

• Example: A customer places an order, which involves multiple microservices such as inventory, payment,...read more
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