Capgemini Java Developer Interview Questions, Process, and Tips

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. SOLID principles in java. Any features in java8 which are there which follows SOLID principle
Ans. 
SOLID principles in Java focus on object-oriented design principles. Java 8 features like lambdas and streams adhere to these principles.
• S - Single Responsibility Principle: Java 8 lambdas allow for defining single-purpose functions.

• O - Open/Closed Principle: Java 8 streams enable extending behavior without modifying existing code.

• L - Liskov Substitution Principle: Java 8 interfaces support polymorphism and substitutio...read more
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Q2. Singleton class in Java. How to write a code in java to make a class singleton
Ans. 
A Singleton class in Java ensures that only one instance of the class is created and provides a global point of access to it.
• Use a private static instance variable to hold the single instance of the class.

• Make the constructor private to prevent instantiation from outside the class.

• Provide a public static method to access the single instance, creating it if necessary.
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Q3. What is a controller.
Ans. 
A controller is a component in the Model-View-Controller (MVC) design pattern that handles user input and updates the model and view accordingly.
• Controls the flow of the application

• Interacts with the model to update data

• Receives input from the user and processes it

• Updates the view based on changes in the model

• Examples: Spring MVC Controller, JavaFX Controller
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Q4. Write a code so that unique elements from an array can be printed
Ans. 
Code to print unique elements from an array of strings
• Create a HashSet to store unique elements

• Iterate through the array and add elements to the HashSet

• Print out the elements in the HashSet to get unique elements
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Q5. Write a code to find the second largest element in an array
Ans. 
Code to find the second largest element in an array
• Iterate through the array and keep track of the largest and second largest elements

• Initialize variables to store the largest and second largest elements

• Compare each element with the largest and second largest elements and update accordingly
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Q6. What is hash collision. From which class is hashCode() and equals() method from
Ans. 
Hash collision occurs when two different inputs produce the same hash value. hashCode() and equals() methods are from Object class.
• Hash collision can occur when two different objects have the same hash code value.

• hashCode() method is used to get the hash code value of an object.

• equals() method is used to compare two objects for equality.
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Q7. Explain circuit breaker, and how to practically implement it
Ans. 
Circuit breaker is a design pattern used to prevent cascading failures in distributed systems.
• Circuit breaker monitors for failures and trips when a threshold is reached

• It then redirects calls to a fallback mechanism to prevent further failures

• Once the system stabilizes, the circuit breaker can be reset to allow normal operation
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Q8. Exception handling in springboot. How to implement controllerAdvice
Ans. 
ControllerAdvice in Spring Boot is used for global exception handling in RESTful APIs.
• Create a class annotated with @ControllerAdvice

• Use @ExceptionHandler to define methods to handle specific exceptions

• Use @RestControllerAdvice for returning JSON responses
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About basic test of knowledge on english & general knowledge

Q1. Questions based on arrays
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Q2. Questions based on strings
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Q3. OOPS concept and threading
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Q4. Multithreading and some coding on array and strings
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Q1. About company policies etc
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Q2. About CTC
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Q1. Coding questions on java8
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Q2. Regarding microservices
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Q3. Internal working of circuit breaker
Ans. 
Circuit breaker is a design pattern used in software development to prevent system failures by temporarily stopping requests to a failing service.
• Circuit breaker monitors the number of failures and opens when a threshold is reached.

• When the circuit is open, requests are not sent to the failing service, preventing further failures.

• After a specified time, the circuit breaker closes and allows requests to be sent again.

• Ex...read more
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Q4. Frequency of occurrence of words
Ans. 
Frequency of occurrence of words in a given text can be calculated by counting each word and storing it in a data structure.
• Split the text into words using whitespace as delimiter

• Create a map to store word frequencies

• Iterate through the words and update the frequency count in the map

• Return the map with word frequencies
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Q5. How spring boot will work two databases
Ans. 
Spring Boot can work with two databases by configuring multiple data sources and using @Primary annotation.
• Configure multiple data sources in application.properties or application.yml

• Use @Primary annotation to specify the primary data source

• Use @Qualifier annotation to specify the secondary data source

• Example: @Configuration @EnableTransactionManagement public class DatabaseConfig { @Primary @Bean(name = "primaryDataSo...read more
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