40+ Atlas Copco Interview Questions and Answers

Securing a Spring Boot application, especially in the context of a banking application, involves implementing Spring Security.

• Use Spring Security to handle authentication and authorization

• Implement secure communication using HTTPS

• Utilize role-based access control to restrict user permissions

• Enable CSRF protection to prevent cross-site request forgery attacks

• Implement secure password storage and session management

Multi-threading is a programming concept where multiple threads run concurrently within a single process.

• Multi-threading allows for parallel execution of tasks, improving performance and responsiveness.

• Used in applications that require handling multiple tasks simultaneously, such as web servers or video editing software.

• Example: Implementing a multi-threaded server to handle multiple client requests concurrently.

ConcurrentModificationException occurs when a collection is modified while iterating over it.

• Occurs in Java when a collection is modified while being iterated over

• Can be resolved by using an Iterator to remove elements instead of directly modifying the collection

• Alternatively, use synchronized collections or ConcurrentHashMap to avoid this exception

CI/CD pipeline automates the process of integrating code changes and deploying them to production.

• Automates the process of integrating code changes

• Automates the process of testing code changes

• Automates the process of deploying code changes

• Helps in detecting and fixing bugs early in the development cycle

• Increases the speed of software delivery

• Ensures consistency in the deployment process

I used AngularJS and Bootstrap to create the UI side of the springboard application.

• AngularJS

• Bootstrap

A key with a null value in HashMap will be stored in the HashMap as a key-value pair with a null value.

• In a HashMap, keys can have null values but only one key with a null value is allowed.

• If you try to store a key with a null value multiple times, the previous value associated with that key will be overwritten.

• Example: HashMap map = new HashMap<>(); map.put(null, 5); // key=null, value=5

Find max and min sum after removing one element from array. Time complexity analysis required.

• Iterate through array to find sum of all elements

• For each element, calculate sum after removing it

• Track max and min sum as you iterate

• Time complexity: O(n) where n is the number of elements in the array

Technologies like Kafka, RabbitMQ, and Apache Pulsar can be used to update microservices with data.

• Kafka

• RabbitMQ

• Apache Pulsar

Multiple data sources in Spring Boot can be handled using Spring Data JPA and configuring multiple data source beans.

• Use @Primary annotation to specify the primary data source bean

• Configure additional data sources in application.properties or application.yml file

• Use @Qualifier annotation to specify which data source to inject in a specific repository or service class

Yes, I typically use a hash set or dictionary to filter out duplicate employee records from a list.

• Iterate through the list of employee records

• Use a hash set or dictionary to keep track of unique employee IDs

• Check each employee record against the hash set or dictionary to filter out duplicates

Implementing an authentication service involves creating a secure system for verifying user identities.

• Use encryption to securely store user passwords

• Implement multi-factor authentication for added security

• Utilize tokens or cookies for session management

• Integrate with OAuth or OpenID Connect for third-party authentication

• Implement rate limiting and account lockout mechanisms to prevent brute force attacks

Integrating Spring Data JPA with Spring Boot allows for easy database operations in a Spring Boot application.

• Add Spring Data JPA dependency in pom.xml

• Create JPA entity classes annotated with @Entity

• Create a repository interface extending JpaRepository

• Use repository interface in service classes for database operations

• Configure application.properties with database connection details

Microservice architecture is a modular approach where an application is divided into smaller, independent services, while monolithic architecture is a single, unified structure.

• Microservice architecture breaks down an application into smaller, loosely coupled services that can be developed, deployed, and scaled independently.

• Monolithic architecture involves building the entire application as a single unit, making it harder to scale and update.

• Microservices communicate through...read more

Custom queries in Spring Data JPA can be created using @Query annotation or method naming conventions.

• Use @Query annotation with JPQL or native SQL to define custom queries

• Follow method naming conventions to automatically generate queries based on method names

• Use parameters in custom queries by adding method parameters and referencing them in the query

To create a repository interface in Spring Data JPA, you need to define an interface that extends JpaRepository.

• Create an interface that extends JpaRepository, where T is the entity type and ID is the type of the entity's primary key.

• Add custom query methods by defining method signatures in the repository interface.

• Spring Data JPA will automatically generate the implementation for the repository interface at runtime.

Custom queries in repository interface are defined using @Query annotation in Spring Data JPA.

• Use @Query annotation above the method declaration in the repository interface.

• Write the custom query in JPQL or native SQL within the @Query annotation.

• You can also pass parameters to the query using method parameters.

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 that return HTML, while @RestController is used to create RESTful web services that return data in JSON or XML format.

• In @RestController, the response body is directly...read more

Communication between microservices can happen through synchronous or asynchronous protocols like HTTP, messaging queues, or gRPC.

• Microservices can communicate through synchronous protocols like HTTP, where one service sends a request to another service and waits for a response.

• Alternatively, microservices can communicate asynchronously using messaging queues like RabbitMQ or Kafka, where messages are sent between services without the need for an immediate response.

• Another me...read more

REST services return data in JSON or XML format.

• Data is typically returned in JSON or XML format.

• JSON is more commonly used due to its simplicity and readability.

• REST services can also return data in other formats like HTML or plain text.

• Example: {"name": "John Doe", "age": 30}

Multithreading in Java allows multiple threads to execute concurrently, improving performance and responsiveness.

• Multithreading allows multiple threads to run concurrently within a single process.

• Each thread has its own stack and program counter, but share the same heap memory.

• Java provides built-in support for multithreading through the java.lang.Thread class.

• Example: Creating a new thread by extending the Thread class or implementing the Runnable interface.

An ID in Hibernate is a unique identifier for an entity in a database. It is used to uniquely identify each record.

• ID is a field in an entity class annotated with @Id in Hibernate.

• It can be of different types like int, long, String, etc.

• ID is used to uniquely identify each record in a database table.

• It is often generated automatically using strategies like @GeneratedValue.

• Example: @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id;

Fail-fast stops immediately upon detecting an error, while fail-safe continues to operate despite errors. Fail-safe is synchronized.

• Fail-fast immediately stops the operation upon encountering an error, ensuring that no further damage is done.

• Fail-safe continues to operate despite errors, often by handling the error and allowing the program to continue running.

• Fail-safe is synchronized, meaning that it is designed to handle errors in a multi-threaded environment.

• An example of ...read more

Some compatible features of Java include platform independence, object-oriented programming, and automatic memory management.

• Platform independence allows Java programs to run on any platform with a Java Virtual Machine (JVM)

• Object-oriented programming allows for modular and reusable code through classes and objects

• Automatic memory management with garbage collection helps manage memory allocation and deallocation

• Java also supports multithreading, exception handling, and networ...read more

Microservices can be updated with new data by using versioning, rolling updates, blue-green deployments, and canary releases.

• Use versioning to manage different versions of microservices.

• Implement rolling updates to gradually update instances without downtime.

• Utilize blue-green deployments to switch between old and new versions seamlessly.

• Employ canary releases to test new data on a small subset of users before full deployment.

To configure login in Spring Boot, you can use Spring Security to handle authentication and authorization.

• Add Spring Security dependency in your pom.xml file

• Create a class that extends WebSecurityConfigurerAdapter to configure security settings

• Override configure(HttpSecurity http) method to define login form, login processing URL, success and failure URLs

• Use @EnableWebSecurity annotation on your main application class to enable Spring Security

To identify an object in a collection, you can iterate through the collection and compare each object with the target object.

• Iterate through the collection using a loop

• Compare each object in the collection with the target object using a conditional statement

• Use a unique identifier or property of the object to match it with the target object

• Example: Identifying a specific student in a list of students by comparing their student ID

Spring Boot actuator provides production-ready features to help monitor and manage your application.

• Provides endpoints to monitor application health, metrics, info, etc.

• Can be used to check the status of the application, database connections, and more.

• Allows customization and security configurations for the endpoints.

Optional in Java is a container object which may or may not contain a non-null value.

• Optional was introduced in Java 8 to handle null values more effectively.

• It is used to avoid NullPointerExceptions by explicitly checking if a value is present before using it.

• Optional can be used with methods that may return null to indicate that the value may be absent.

• Example: Optional optionalName = Optional.ofNullable(name);

JDK is a development kit for creating Java applications, while JRE is a runtime environment for executing Java programs.

• JDK stands for Java Development Kit and includes tools for developing Java applications, such as compiler and debugger.

• JRE stands for Java Runtime Environment and is used to run Java applications. It includes JVM, libraries, and other necessary components.

• JDK is needed for developing Java applications, while JRE is needed for running Java applications.

• Exampl...read more

HashMap in Java 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 its index in the array.

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

• HashMap allows null keys and values, and does not guarantee the order of key-value pairs.

DispatcherServlet is the front controller in Spring Boot that receives incoming requests and dispatches them to the appropriate handler.

• DispatcherServlet is a servlet that manages the flow of incoming requests in a Spring Boot application.

• It acts as the front controller, receiving all requests and then dispatching them to the appropriate handler for processing.

• DispatcherServlet is configured in the web.xml file or through Java configuration.

• It is responsible for handling the ...read more

Yes, microservices can contain transactional data.

• Microservices can handle transactional data by using distributed transactions or event sourcing.

• Each microservice can manage its own database, which can include transactional data.

• Microservices can communicate with each other to ensure consistency in transactional data.

• Examples: E-commerce platform with separate microservices for inventory, orders, payments, etc.

No, Java programs require JRE to run.

• Java programs are compiled into bytecode which is executed by the Java Runtime Environment (JRE)

• JRE is necessary to interpret and run Java programs

• Without JRE, Java programs cannot be executed

Executor framework in Java is a framework that provides a way to manage and control the execution of tasks in a multithreaded environment.

• Allows for decoupling task submission from task execution

• Provides a way to manage thread creation, pooling, and scheduling of tasks

• Helps in handling exceptions and errors that occur during task execution

• Examples include ThreadPoolExecutor and ScheduledThreadPoolExecutor classes

The join method in Java is used to concatenate the elements of an array into a single string.

• The join method is a part of the String class in Java.

• It takes an array of strings as input and concatenates them with a specified delimiter.

• Example: String[] arr = {"Hello", "World"}; String result = String.join(", ", arr); // Output: Hello, World

One-to-many and many-to-one relationships in Hibernate are used to define the relationship between entities in a database.

• One-to-many relationship: One entity can be associated with multiple instances of another entity. For example, one department can have multiple employees.

• Many-to-one relationship: Multiple instances of one entity can be associated with a single instance of another entity. For example, multiple employees can belong to one department.

Messaging between microservices involves communication through message brokers or direct API calls.

• Microservices communicate through message brokers like RabbitMQ or Kafka.

• Messages are sent in a format like JSON or XML.

• Microservices can also communicate through direct API calls using REST or gRPC.

• Message queues help in decoupling services and ensuring reliable communication.

• Service discovery mechanisms like Consul or Eureka help in locating services for messaging.

Some common annotations used in Spring Boot are @RestController, @Autowired, @RequestMapping, @Component, @Service, @Repository.

• @RestController - Used to define a controller class in Spring MVC.

• @Autowired - Used for automatic dependency injection.

• @RequestMapping - Used to map web requests to specific handler methods.

• @Component - Indicates that a class is a Spring component.

• @Service - Indicates that a class is a Spring service.

• @Repository - Indicates that a class is a Spring r...read more

Some methods in Executor framework include execute(), submit(), shutdown(), awaitTermination(), and invokeAll().

• execute() - Used to execute the given command at some time in the future.

• submit() - Submits a Runnable or Callable task for execution and returns a Future representing the task.

• shutdown() - Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted.

• awaitTermination() - Blocks until all tasks have completed execu...read more

Microservices are a software development technique where applications are composed of small, independent services that communicate with each other.

• Microservices are small, focused services that work together to form a complete application

• Each microservice is responsible for a specific function or feature

• Microservices communicate with each other through APIs

• Microservices can be developed, deployed, and scaled independently

• Examples of companies using microservices include Netfl...read more

A Daemon thread is a background thread that runs without blocking the main program from exiting.

• Daemon threads are used for tasks that do not require user interaction or continuous monitoring.

• They are automatically terminated by the JVM when all non-daemon threads have finished.

• An example of a Daemon thread is the garbage collector in Java.

Spring Boot is a Java-based framework used to create standalone, production-grade Spring-based applications.

• Spring Boot simplifies the process of creating and deploying Spring applications.

• It provides a set of pre-configured tools and conventions to get started quickly.

• Spring Boot includes embedded servers like Tomcat, Jetty, or Undertow for easy deployment.

• It allows for easy configuration through properties files or YAML.

• Spring Boot also offers built-in support for security,...read more

REST API is a set of rules and conventions for building and interacting with web services.

• REST stands for Representational State Transfer

• Uses standard HTTP methods like GET, POST, PUT, DELETE

• Communicates over HTTP using JSON or XML

• Stateless, meaning each request from a client to server must contain all the information needed to understand the request

HashMap is unordered while LinkedHashMap maintains insertion order.

• HashMap does not maintain insertion order while LinkedHashMap does.

• LinkedHashMap extends HashMap and adds a doubly-linked list to maintain order.

• HashMap is faster for iteration while LinkedHashMap is slower due to maintaining order.

Load factor in HashMap determines when the HashMap should be resized to maintain performance.

• Load factor is a measure of how full the HashMap is allowed to get before its capacity is automatically increased.

• The default load factor of HashMap is 0.75, which means the HashMap will be resized when it is 75% full.

• Increasing the load factor reduces the space overhead but increases the time cost of resolving collisions.

• Example: If a HashMap has a capacity of 16 and a load factor of...read more