Jio Java Developer Interview Questions and Answers

Q1. What improvements to interfaces were introduced in Java 8 that were missing in Java 7, specifically regarding static and default methods?
Ans. 
Java 8 introduced static and default methods in interfaces, allowing for method implementation and code reusability.
• Java 8 introduced static methods in interfaces, allowing for method implementation directly in the interface itself.

• Default methods were also introduced in Java 8, enabling interfaces to have method implementations without affecting implementing classes.

• Static methods in interfaces can be called using the...read more
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Q2. Explain internal working of HashMap ? How to synchronize it ?
Ans. 
HashMap is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values.
• HashMap uses an array of linked lists to store key-value pairs.

• When a key-value pair is added, the key is hashed to determine the index in the array where it will be stored.

• If multiple keys hash to the same index, a linked list is used to handle collisions.

• To synchronize a HashMap, you can use the synchronizedMap() m...read more
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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?
Ans. 
No, the program will not compile if the parent class throws a runtime exception while the child class throws an arithmetic exception.
• In Java, if a parent class method throws a checked exception, the child class method can only throw the same exception or its subclasses.

• ArithmeticException is an unchecked exception, so if the parent class throws a checked exception and the child class throws an unchecked exception, the ...read more
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Q5. In a Spring Boot application with two databases, how can you configure JDBC to specify which database to use?
Ans. 
Configure JDBC in Spring Boot to specify which database to use
• Define multiple DataSource beans in the configuration class

• Use @Primary annotation to specify the primary DataSource

• Use @Qualifier annotation to specify the secondary DataSource

• Inject the DataSource beans where needed in the application
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Q6. How to use a jetty server in your spring boot application ?
Ans. 
To use a Jetty server in a Spring Boot application, you can configure it as a dependency and customize its settings.
• Add Jetty server dependency in your pom.xml file

• Exclude Tomcat server dependency if it's included by default in Spring Boot

• Configure Jetty server settings in application.properties or application.yml file

• Example: Add Jetty dependency - <dependency> <groupId>org.springframework.boot</groupId...read more
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Q7. Difference between @RequestParam and @PathVariable ?
Ans. 
RequestParam is used to extract query parameters from the URL, while PathVariable is used to extract values from the URI path.
• RequestParam is used for query parameters in the URL, while PathVariable is used for values in the URI path.

• RequestParam is optional, while PathVariable is required.

• RequestParam is used with the @RequestParam annotation, while PathVariable is used with the @PathVariable annotation.

• Example: @Requ...read more
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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?
Ans. 
I would implement timeout mechanisms and retries to handle the scenario of one microservice awaiting a response from another microservice taking an extended time.
• Implement timeout mechanisms in the calling microservice to limit the waiting time for a response.

• Set up retry logic to automatically resend the request to the slow microservice if no response is received within the specified timeout period.

• Use circuit breaker...read more
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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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Q1. Java streams on students
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Q2. Select 8 form A,A
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Q3. Basic java questions
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Q4. Hibernate questions and database questions
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It had java programming and aptitude tests and MCQs

Q1. Asked SQL, microservices and java questions
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Q1. Difference between hashmap and hash table
Ans. 
HashMap is non-synchronized and allows null values, while HashTable is synchronized and does not allow null values.
• HashMap is non-synchronized, meaning it is not thread-safe, while HashTable is synchronized and thread-safe.

• HashMap allows null values for both keys and values, while HashTable does not allow null keys or values.

• HashMap is generally preferred for non-thread-safe applications, while HashTable is used in mul
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Q2. Static block related questions
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Q3. Arraylist and linkedlist question
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Onlin test consist pf easy numerical questions

Easy questions not so difficult

Q1. Java oops concept
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Q2. Basic sprophramming questions
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Q3. Networking firewall cisco
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Q1. Personal questions
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Q2. Whetehr to willing to work in any locations
Ans. 
Yes, I am willing to work in any location for the right opportunity.
• I am open to relocating for the right job opportunity

• I am flexible and adaptable to new environments

• I believe working in different locations can provide valuable experiences and growth opportunities
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