70+ Senior Application Developer Interview Questions and Answers

Design a Least Recently Used (LRU) cache data structure that supports get and put operations with capacity constraint.

• Implement a doubly linked list to keep track of the order of keys based on their recent usage.

• Use a hashmap to store key-value pairs for quick access and update.

• When capacity is reached, evict the least recently used item before inserting a new item.

• Handle get and put operations efficiently to maintain the LRU property.

• Ensure the time complexity of operations ...read more

Convert a binary tree to a sum tree by replacing each node with the sum of its left and right subtrees, setting leaf nodes to zero.

• Traverse the tree in postorder fashion to calculate the sum of left and right subtrees for each node.

• Set leaf nodes to zero by checking if a node has no children.

• Update the value of each node to be the sum of its left and right subtrees.

• Return the level order traversal of the converted sum tree.

Autowiring in Spring Boot is a feature that allows Spring to automatically inject dependencies into a Spring bean.

• Autowiring eliminates the need for explicit bean wiring in the Spring configuration file.

• There are different modes of autowiring in Spring Boot: 'byName', 'byType', 'constructor', 'autodetect', and 'no'.

• For example, 'byName' autowiring matches and injects a bean based on the name of the bean property.

Find the node where two linked lists merge, return -1 if no merging occurs.

• Traverse both lists to find their lengths and the difference in lengths

• Move the pointer of the longer list by the difference in lengths

• Traverse both lists simultaneously until they meet at the merging point

SOLID principles are a set of five design principles in object-oriented programming to make software designs more understandable, flexible, and maintainable.

• S - Single Responsibility Principle: A class should have only one reason to change.

• O - Open/Closed Principle: Software entities should be open for extension but closed for modification.

• L - Liskov Substitution Principle: Objects of a superclass should be replaceable with objects of its subclasses without affecting the corr...read more

setMaxResults() limits the number of results returned by a query, while setFetchSize() determines the number of rows fetched at a time from the database.

• setMaxResults() is used to limit the number of results returned by a query.

• setFetchSize() determines the number of rows fetched at a time from the database.

• setMaxResults() is typically used for pagination purposes, while setFetchSize() can improve performance by reducing the number of round trips to the database.

• Example: setM...read more

Optional class in Java provides a way to handle null values more effectively.

• Prevents NullPointerException by explicitly checking for null values

• Encourages developers to handle null values properly

• Improves code readability and maintainability

• Helps avoid unnecessary null checks and nested if statements

The @RestController annotation in Spring Boot is used to define a class as a RESTful controller.

• Used to create RESTful web services in Spring Boot

• Combines @Controller and @ResponseBody annotations

• Eliminates the need to annotate each method with @ResponseBody

Standard Java pre-defined functional interfaces include Function, Consumer, Predicate, Supplier, etc.

• Function: Represents a function that accepts one argument and produces a result. Example: Function<Integer, String>

• Consumer: Represents an operation that accepts a single input argument and returns no result. Example: Consumer<String>

• Predicate: Represents a predicate (boolean-valued function) of one argument. Example: Predicate<Integer>

• Supplier: Represents a supplier of result...read more

Abstraction in OOP is the concept of hiding complex implementation details and showing only the necessary features of an object.

• Abstraction allows developers to focus on what an object does rather than how it does it

• It helps in reducing complexity and improving code reusability

• Example: In a car object, we only need to know how to drive it (interface) without worrying about the internal engine workings (implementation)

Spring Cloud addresses issues related to microservices architecture and cloud-native applications.

• Service discovery and registration

• Load balancing

• Circuit breakers

• Distributed messaging

• Configuration management

• Fault tolerance

• Monitoring and tracing

Spring supports five bean scopes: singleton, prototype, request, session, and application.

• Singleton scope: Default scope, only one instance per Spring container

• Prototype scope: New instance created each time bean is requested

• Request scope: Bean is created once per HTTP request

• Session scope: Bean is created once per HTTP session

• Application scope: Bean is created once per ServletContext

Hibernate provides several concurrency strategies like optimistic locking, pessimistic locking, and versioning.

• Optimistic locking: Allows multiple transactions to read and write to the database without locking the data. It checks for conflicts before committing the transaction.

• Pessimistic locking: Locks the data when a transaction reads it, preventing other transactions from accessing it until the lock is released.

• Versioning: Uses a version number to track changes to an entit...read more

The @SpringBootApplication annotation is used to mark a configuration class that declares one or more @Bean methods and also triggers auto-configuration and component scanning.

• Marks a class as a Spring Boot application

• Enables auto-configuration of the Spring application context

• Performs component scanning for Spring components

• Combines @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations

Yes, it is possible to import the same class or package twice in Java, but it will not cause any issues during runtime.

• Importing the same class or package multiple times in Java will not result in any errors or conflicts.

• The Java compiler will simply ignore duplicate imports and only include the class or package once in the compiled code.

• This behavior helps in avoiding unnecessary redundancy and keeps the code clean and concise.

Java Strings are immutable to ensure data integrity, thread safety, and security.

• Immutable strings prevent accidental modification of data.

• String pool optimization is possible due to immutability.

• Thread safety is ensured as strings cannot be modified concurrently.

• Security is enhanced as sensitive information cannot be altered.

MVC components include Model, View, and Controller for organizing code in a web application.

• Model: Represents the data and business logic of the application.

• View: Represents the UI and presentation layer of the application.

• Controller: Acts as an intermediary between Model and View, handling user input and updating the Model accordingly.

• Example: In a web application, a user interacts with the View (UI), which sends requests to the Controller. The Controller processes the reque...read more

I will use try-catch blocks to handle exceptions and log the error message for debugging purposes.

• Enclose the procedure call in a try block.

• Catch the exception in the catch block.

• Log the error message for debugging purposes.

• Handle the exception appropriately based on the specific scenario.

Marker interfaces in Java are interfaces with no methods, used to mark classes for special treatment.

• Marker interfaces have no methods, they simply mark a class as having a certain capability or characteristic.

• Examples of marker interfaces in Java include Serializable, Cloneable, and Remote.

• Classes implementing marker interfaces can be treated differently by the JVM or other components based on the interface they implement.

When passing an object as the key in a map, extra functionality needs to be implemented to ensure proper hashing and equality comparison.

• Override hashCode() method to generate a unique hash code for the object

• Override equals() method to compare the objects for equality

• Implement Comparable interface if custom sorting is required

A classloader in Java is a part of the Java Runtime Environment that dynamically loads Java classes into the Java Virtual Machine.

• Classloaders are responsible for loading classes at runtime based on the fully qualified name of the class.

• There are different types of classloaders in Java such as Bootstrap Classloader, Extension Classloader, and Application Classloader.

• Classloaders follow a delegation model where a classloader delegates the class loading to its parent classloade...read more

Use a routing library like React Router to manage navigation and organize components into separate pages.

• Utilize React Router to set up routes for each page and handle navigation

• Organize components into separate folders based on their functionality or page they belong to

• Consider lazy loading components to improve performance, especially with a large number of pages

Functional interfaces can have only one abstract method, but can have multiple static and default methods.

• Functional interfaces in Java can have only one abstract method, but can have multiple static and default methods.

• Static methods in functional interfaces can be called using the interface name itself.

• Default methods provide a default implementation in the interface itself.

• Example: java.util.function.Function is a functional interface with one abstract method and default m...read more

Filters in MVC are components that allow pre-processing and post-processing of requests and responses.

• Filters are used to perform common functionalities like logging, authentication, authorization, etc.

• They can be applied globally to all controllers or selectively to specific controllers or actions.

• Examples of filters include Authorization filters, Action filters, Result filters, and Exception filters.

Implemented a complex data migration from legacy system to new system

• Identified all data sources and mapped them to new system

• Developed custom scripts to transform and validate data

• Performed multiple test runs to ensure data integrity

• Coordinated with stakeholders to ensure smooth transition

Routing in MVC pattern is handled by a routing engine which maps incoming URLs to specific controller actions.

• Routing is the process of matching incoming URLs to specific controller actions in the MVC pattern.

• Routes are defined in a routing table which maps URLs to corresponding controller actions.

• The routing engine uses the routing table to determine which controller and action should handle a particular request.

• Routes can include placeholders for dynamic segments of the URL...read more

Garbage collector in Java is a built-in mechanism that automatically manages memory by reclaiming unused objects.

• Garbage collector runs in the background to identify and delete objects that are no longer needed.

• It helps prevent memory leaks and optimize memory usage.

• Examples of garbage collectors in Java include Serial, Parallel, CMS, and G1.