HCLTech Core Java Developer Interview Questions and Answers

Q1. Tell me something about my self
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Q2. Why should we hire you
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Q3. Salary expectation
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Q1. What improvements to interfaces were introduced in Java 8 that were missing in Java 7, specifically regarding static and default methods?
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Q2. Explain internal working of HashMap ? How to synchronize it ?
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Q3. Given a list of employees with their ratings, how can you sort the employees based on their ratings using the Java 8 Streaming API?
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Q4. Will the program compile if the parent class throws a runtime exception while the child class throws an arithmetic exception?
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Q5. In a Spring Boot application with two databases, how can you configure JDBC to specify which database to use?
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Q6. How to use a jetty server in your spring boot application ?
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Q7. Difference between @RequestParam and @PathVariable ?
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Q8. How would you handle a scenario where one microservice is awaiting a response from another microservice that is taking an extended time to respond?
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Q1. Create one Spring boot controller from end to end. No need to create a spring boot project we just want to see the structure and end to end implementation.
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Q2. Write a java 8 program to get the characters from a string whose count is 2 or more than 2 e.g. input: baseball , output: b, a, l.
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Q3. Why you left your previous organization.
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Q4. What is the functional interface
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Q5. What are the OOPS concepts. and some questions related to inheritance.
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Q6. Asked about the project mentioned in CV (Client project) and asked its architecture.
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Q7. Various SQL join types
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Q1. Are you ready to relocate to job location
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Q2. Why are you leaving your previous organization.
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Q3. Expectation about salary
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Q1. Java 8 , java 11 and java 17 features?
Ans. 
Java 8 introduced lambda expressions, Java 11 added local-variable syntax for lambda parameters, and Java 17 included sealed classes and pattern matching.
• Java 8 introduced lambda expressions for functional programming.

• Java 11 added local-variable syntax for lambda parameters to simplify code.

• Java 17 included sealed classes to restrict inheritance and pattern matching for instanceof checks and type casts.
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Q2. Dispatcher servlet, design patterns
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Q3. @SpringbootApplication annotation, actuators
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Q4. String Coding question with java 8 features such as lambda function and stream api
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Q5. Number of words in a string
Ans. 
Count the number of words in a given string.
• Split the string by spaces and count the number of resulting elements.

• Handle edge cases like multiple spaces or empty strings.

• Consider punctuation marks as part of words unless specified otherwise.
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Q6. Microservice design patterns
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It's walkin, so they conducted 1 technical mcqs round.

Q1. Multi threading
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Q2. Internal working of hashmap
Ans. 
HashMap in Java is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values based on keys.
• HashMap uses an array of buckets to store key-value pairs.

• Keys are hashed to determine the index in the array where the key-value pair will be stored.

• In case of hash collisions, a linked list or a balanced tree is used to store multiple key-value pairs in the same bucket.

• HashMap allows null keys...read more
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Q3. Spring batch related
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Q4. Non repeating characters in a array
Ans. 
Function to find and return all non-repeating characters in an array of strings.
• Iterate through the array and count the occurrences of each character using a HashMap.

• Then iterate through the array again and check if the count of each character is 1, if so add it to the result list.

• Return the list of non-repeating characters.
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Q5. 3rd highest salary
Ans. 
To find the 3rd highest salary in a database, we can use a SQL query with the 'LIMIT' and 'OFFSET' keywords.
• Use a SQL query with 'ORDER BY salary DESC' to sort the salaries in descending order.

• Use 'LIMIT 1 OFFSET 2' to skip the first two highest salaries and retrieve the third highest salary.

• Example: SELECT salary FROM employees ORDER BY salary DESC LIMIT 1 OFFSET 2;
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Q6. Qualifier vs primary
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A qualifier in Java is used to specify additional information about a primary, which is the main data type or variable.
• A primary in Java is the main data type or variable, while a qualifier provides additional information about the primary.

• Qualifiers can be used to modify the behavior or characteristics of a primary.

• For example, in Java, 'final' is a qualifier that can be used to make a variable constant.
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Q7. Controller vs restcontroller
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The main difference is that @RestController is a specialized version of @Controller that is used for RESTful web services.
• Both @Controller and @RestController are used in Spring MVC to handle HTTP requests, but @RestController is specifically used for RESTful web services.

• @Controller is used to create web pages, while @RestController is used to return data in JSON or XML format.

• @RestController is a convenience annotati...read more
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Q8. Spring boot annotataions
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Q9. Oops concepts with examples
Ans. 
OOP concepts include inheritance, encapsulation, polymorphism, and abstraction.
• Inheritance: Allows a class to inherit properties and behavior from another class. Example: class Dog extends Animal.

• Encapsulation: Bundling data and methods that operate on the data into a single unit. Example: private variables with public getter and setter methods.

• Polymorphism: Ability for objects to be treated as instances of their paren...read more
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Q10. Spring batch configuration
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Q11. They covered all java, spring and Microservices
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Q1. Microservices architecture
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Q2. How do Microservices communicate
Ans. 
Microservices communicate with each other through various communication protocols like HTTP, messaging queues, and gRPC.
• Microservices can communicate over HTTP using RESTful APIs.

• Messaging queues like RabbitMQ or Kafka can be used for asynchronous communication between microservices.

• gRPC is a high-performance, open-source RPC framework that can be used for communication between microservices.

• Service discovery mechanism...read more
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Q3. How to access the Microservice end point
Ans. 
Microservice endpoints can be accessed using HTTP requests with the appropriate URL
• Use HTTP methods like GET, POST, PUT, DELETE to interact with the microservice

• Construct the URL with the base URL of the microservice and the specific endpoint path

• Include any necessary headers or parameters in the request for authentication or data filtering
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Q4. Why we use microservices
Ans. 
Microservices allow for modular, scalable, and flexible software development by breaking down applications into smaller, independent services.
• Microservices enable easier maintenance and updates as each service can be developed, deployed, and scaled independently.

• They improve fault isolation, as failures in one service do not necessarily affect the entire application.

• Microservices promote agility and faster time-to-mark...read more
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Q1. What are intermediate and terminal operations
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Q2. Predefined functional interface
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Q3. Ways to create Thread
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