80+ Java Full Stack Developer Interview Questions and Answers

Creating immutable class of orders, sorting orders, finding average of lists of integers.

• Create an immutable class Orders with private final fields and no setter methods.

• Override equals() and hashCode() methods to ensure uniqueness of objects.

• Use Collections.unmodifiableSet() to create a set of orders and Collections.sort() to sort them.

• Iterate through the List of List of String of integers, convert to integers, and calculate average for each list.

Method overloading is having multiple methods with the same name but different parameters. Method overriding is having a method in the subclass with the same name and parameters as in the superclass.

• Method overloading is done in the same class while method overriding is done in different classes.

• Method overloading is used to provide different ways of calling the same method while method overriding is used to provide a specific implementation of a method in the subclass.

• Method...read more

Microservices are connected in REST APIs using communication protocols like HTTP, messaging queues, and service discovery.

• Microservices communicate with each other using HTTP requests and responses.

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

• Service discovery tools like Eureka or Consul help in locating and connecting to different microservices.

• API Gateway can be used to aggregate multiple microservices into a singl...read more

Spring Cloud is a set of tools and frameworks for building cloud-native applications in Java.

• Spring Cloud provides tools for service discovery, load balancing, configuration management, and more in microservices architecture.

• It includes projects like Eureka for service discovery, Ribbon for client-side load balancing, and Config Server for externalized configuration.

• Spring Cloud integrates with Spring Boot to simplify the development of distributed systems.

• Using Spring Cloud,...read more

The class will have to provide its own implementation of the conflicting default method.

• When implementing multiple interfaces with the same default method, a class must provide its own implementation of the conflicting method.

• The class cannot inherit the default implementation from both interfaces.

• The class can choose to implement one of the default methods and provide its own implementation for the other.

• Alternatively, the class can provide a completely new implementation fo...read more

Exception handling in Spring Boot project

• Use @ExceptionHandler annotation to handle exceptions

• Use @ControllerAdvice to handle exceptions globally

• Use try-catch block to handle exceptions in specific methods

• Use ResponseEntity to return custom error messages

• Use logging to track and debug exceptions

The shortest distance from the starting point is 5 km.

• The person walks 3 km towards west, forming a right angle triangle with the starting point.

• Then the person turns left and walks 4 km, forming another side of the right angle triangle.

• The shortest distance from the starting point is the hypotenuse of the right angle triangle, which can be calculated using Pythagoras theorem as sqrt(3^2 + 4^2) = 5 km.

Microservices architecture is a design approach where a single application is composed of small, independent services that communicate with each other.

• Each microservice is responsible for a specific business function or capability

• Microservices communicate with each other through APIs

• Each microservice can be developed, deployed, and scaled independently

• Microservices architecture promotes flexibility, scalability, and resilience

• Examples: Netflix, Amazon, Uber

Microservices are a software development technique where an application is divided into smaller, independent services that communicate with each other through APIs.

• Microservices are small, independent services that focus on specific business functions.

• Each microservice can be developed, deployed, and scaled independently.

• Microservices communicate with each other through APIs, typically using lightweight protocols like HTTP or messaging queues.

• They promote flexibility, scalabi...read more

Inheritance is a mechanism in OOP where a new class is derived from an existing class.

• It allows code reusability and saves time and effort in writing code.

• The derived class inherits the properties and methods of the base class.

• The derived class can also add new properties and methods or override the existing ones.

• It helps in achieving polymorphism and abstraction.

• Example: A Car class can be inherited by a SportsCar class which can add new properties like top speed and overrid...read more

Yes, I am willing to work on new technologies that are not yet in the market.

• I am always eager to learn and adapt to new technologies to stay ahead in the industry.

• Working on emerging technologies can provide valuable experience and opportunities for growth.

• Examples of technologies I am interested in exploring include blockchain, quantum computing, and artificial intelligence.

Optional class is used to handle null values in Java 8 and above.

• Optional class is a container object that may or may not contain a non-null value.

• It provides methods to check if a value is present or not, and to retrieve the value if it is present.

• It helps to avoid NullPointerExceptions and makes the code more readable and concise.

• Example: Optional name = Optional.ofNullable(person.getName());

• If person.getName() returns null, then name will be an empty Optional object.

To compare two objects with the same class, override the equals and hashCode methods in the class.

• Override the equals method to compare the fields of the objects for equality.

• Override the hashCode method to generate a unique hash code based on the object's fields.

• Ensure that the equals and hashCode methods are consistent with each other.

• Example: public class Person { private String name; private int age; }

Data binding in Angular allows automatic synchronization of data between the model and the view.

• Interpolation: {{ }} - binds data from the component to the view

• Property binding: [] - binds data from the component to an element property

• Event binding: () - binds an event from the view to a method in the component

• Two-way binding: [()] - combines property and event binding to achieve two-way data flow

Inline templates are used for small, simple templates, while external templates are used for larger, complex templates.

• Inline templates are defined within the component's TypeScript file using the template property.

• External templates are defined in separate HTML files and linked to the component using the templateUrl property.

• Inline templates are useful for small components or when the template is simple and doesn't require much HTML code.

• External templates are beneficial for...read more

React is a JavaScript library for building user interfaces.

• React is component-based, meaning UI is broken down into reusable pieces

• Components can have states, which are mutable data that affect rendering

• Redux is a state management library that can be used with React

• Redux helps manage complex states and data flow in larger applications

DELETE command removes specific rows from a table, while TRUNCATE command removes all rows from a table.

• DELETE command is used to remove specific rows from a table based on a condition.

• TRUNCATE command is used to remove all rows from a table, resetting auto-increment values.

• DELETE command is slower as it logs individual row deletions, while TRUNCATE is faster as it does not log individual deletions.

• DELETE can be rolled back using a transaction, while TRUNCATE cannot be rolled...read more

To connect JPA and update values from the database, you need to use entity manager and transactions.

• Create an entity class representing the table in the database

• Use EntityManager to retrieve the entity from the database

• Update the values of the entity

• Begin a transaction, commit the transaction after updating the values

Spring Framework is a popular Java framework for building enterprise applications. Microservices are a software development technique that structures an application as a collection of loosely coupled services. MySQL is a relational database management system, while MongoDB is a NoSQL database.

• Spring Framework is a comprehensive framework that provides support for developing Java applications. It offers features like dependency injection, aspect-oriented programming, and more....read more

Check if a string containing only specific characters is valid by ensuring all opening brackets have corresponding closing brackets.

• Use a stack to keep track of opening brackets and pop when a closing bracket is encountered.

• If stack is empty at the end, return true. Otherwise, return false.

• Example: Input: '()[]{}', Output: true

An object is a physical entity in memory, while an instance is a specific realization of an object.

• An object is a general concept, while an instance is a specific occurrence of that concept.

• Objects are created using classes, while instances are created using the 'new' keyword.

• Each instance has its own state (values of attributes) and behavior (methods).

• Example: 'Car' is an object, while 'Toyota Camry' is an instance of the 'Car' object.

Multiply two arrays element-wise.

• Loop through both arrays and multiply each element at the same index.

• Store the result in a new array.

• Return the new array.

The two types of compiler in Angular are JIT (Just-in-Time) compiler and AOT (Ahead-of-Time) compiler.

• JIT compiler compiles the code at runtime in the browser.

• AOT compiler compiles the code before the application is deployed to the browser.

• JIT compilation is slower but allows for faster development and debugging.

• AOT compilation is faster but requires additional build step before deployment.

HttpClient module is used for http calls in Angular.

• HttpClient module is part of the @angular/common/http package.

• It provides a simplified API for making HTTP requests.

• It supports various HTTP methods like GET, POST, PUT, DELETE, etc.

• It also supports features like request/response headers, query parameters, error handling, etc.

• Example: import { HttpClient } from '@angular/common/http';

Builder/Factory Pattern is used to create objects with complex initialization logic.

• Builder Pattern separates the construction of a complex object from its representation.

• Factory Pattern creates objects without specifying the exact class of object that will be created.

• Builder Pattern is often used to create immutable objects with many optional parameters.

• Factory Pattern is used when there is a need to create multiple instances of a class with similar characteristics.

Java is a backend language, Javascript is a frontend language. Synchronization in Java ensures only one thread can access a resource at a time. JavaScript is single-threaded but can handle asynchronous operations using callbacks, promises, and async/await.

• Java is a backend language used for server-side development, while JavaScript is a frontend language used for client-side scripting.

• Synchronization in Java is a technique that allows only one thread to access a shared resour...read more

A Pojo class is a simple Java class that contains only private fields, public getters and setters, and no-arg constructor.

• Create private fields for employee details like name, id, salary, etc.

• Generate public getters and setters for each field.

• Include a no-arg constructor in the class.

• Example: public class Employee { private String name; private int id; public String getName() { return name; } public void setName(String name) { this.name = name; } public int getId() { return i...read more

Deployment build config includes settings for deploying the application.

• Use tools like Maven or Gradle to manage dependencies and build the project

• Specify deployment environment configurations in a separate file (e.g. application.properties)

• Define build scripts for tasks like compiling, packaging, and deploying the application

• Leverage CI/CD pipelines for automated builds and deployments

Java Full Stack Developer should have knowledge of both front-end and back-end development using Java technologies.

• Java programming language

• Spring Framework

• Hibernate

• HTML/CSS/JavaScript

• RESTful APIs

• Database management

• Version control systems

AI is a broader concept of machines being able to carry out tasks in a smart way, while ML is a subset of AI that allows machines to learn from data.

• AI is the broader concept of machines being able to carry out tasks in a smart way, often involving decision-making and problem-solving.

• ML is a subset of AI that focuses on the development of computer programs that can access data and use it to learn for themselves.

• AI can involve various techniques like rule-based systems, expert...read more

Projections in Spring Data JPA allow customizing the shape of the data returned from a query.

• Projections are used to retrieve specific fields or a subset of fields from an entity.

• They help in reducing the amount of data transferred over the network.

• Projections can be defined using interfaces or classes.

• They can be used with both JPQL and native SQL queries.

• Projections can be used to fetch related entities as well.

A database system for gym management system

• Create tables for members, trainers, classes, and equipment

• Include columns for personal information, membership status, and payment history

• Track attendance, class schedules, and equipment maintenance

• Implement security measures to protect sensitive information

Routes in React js are used to define the navigation paths and handle the rendering of different components based on the URL.

• Routes are defined using the React Router library

• Each route is associated with a specific URL path and a corresponding component

• When a user navigates to a specific URL, the corresponding component is rendered

• Routes can also have parameters that can be accessed in the component

• Nested routes can be defined to create complex navigation structures

Spring Boot provides various annotations for different purposes.

• The @RestController annotation is used to create RESTful web services.

• The @Autowired annotation is used for automatic dependency injection.

• The @RequestMapping annotation is used to map HTTP requests to specific methods.

• The @Component annotation is used to mark a class as a Spring component.

• The @Service annotation is used to mark a class as a Spring service.

• The @Repository annotation is used to mark a class as a S...read more

To create a button in HTML, use the <button> tag with the desired text or image inside.

• Use the <button> tag to create a button element

• Add text or image inside the <button> tag to display on the button

• Specify any desired attributes like id, class, onclick event, etc. for the button

Factorial in C can be calculated using a recursive function or a loop.

• Use a recursive function to calculate factorial

• Use a loop to calculate factorial

• Handle edge cases like 0 and negative numbers

Yes, code optimization can improve performance, reduce memory usage, and enhance readability.

• Optimizing algorithms and data structures can improve performance.

• Minimizing redundant code and using efficient coding techniques can reduce memory usage.

• Refactoring code to make it more readable and maintainable can enhance code quality.

• Using appropriate design patterns and libraries can optimize code.

• Profiling and benchmarking code can help identify areas for optimization.

Creating an Entity Class in Java

• Define class with @Entity annotation

• Add @Id annotation for primary key

• Include fields with appropriate data types

A class is a blueprint for creating objects in Java, while an object is an instance of a class.

• A class defines the properties and behaviors of objects.

• An object is created using the 'new' keyword followed by the class name.

• Multiple objects can be created from the same class.

I have worked with various design patterns such as Singleton, Factory, Observer, and MVC.

• Implemented Singleton pattern to ensure only one instance of a class exists

• Utilized Factory pattern to create objects without specifying the exact class

• Implemented Observer pattern to establish a one-to-many dependency between objects

• Utilized MVC pattern to separate the concerns of data, presentation, and user input

Sorting integers in an array using various sorting algorithms.

• Use built-in sorting methods like Arrays.sort() for quick implementation.

• Implement sorting algorithms like Bubble Sort, Selection Sort, Merge Sort, etc. for learning purposes.

• Consider the time complexity of the sorting algorithm when choosing the best approach.

Java is a widely used programming language known for its platform independence and versatility.

• Java is platform independent, meaning it can run on any device with a Java Virtual Machine (JVM)

• Java is versatile and can be used for developing a wide range of applications such as web, mobile, desktop, and enterprise applications

• Java has a large and active community, providing support, resources, and libraries for developers

• Java is known for its performance, security, and scalabil...read more

Redux is used in React to manage the application state in a predictable way.

• Centralized state management for React applications

• Predictable state changes with actions and reducers

• Easier debugging and testing of state changes

• Facilitates communication between components

Garbage collector is a program in Java that automatically manages memory by reclaiming unused memory.

• Garbage collector runs in the background and identifies objects that are no longer needed.

• It frees up memory by removing these unused objects, making the memory available for new objects.

• There are different types of garbage collectors in Java such as Serial, Parallel, CMS, G1, etc.

Terminal operations in streams produce a result or a side effect, while intermediate operations transform or filter the data.

• Terminal operations are the final operations in a stream pipeline, such as forEach, collect, or reduce.

• Intermediate operations are operations that can be chained together, such as filter, map, or sorted.

• Terminal operations trigger the processing of the stream and produce a result or a side effect.

• Intermediate operations transform or filter the data in t...read more

Find the most occurred letter in a given string.

• Iterate through the string and count the occurrences of each letter

• Store the counts in a map or array

• Find the letter with the highest count

Java is a high-level programming language known for its platform independence and object-oriented features.

• Java is platform-independent, meaning it can run on any device with a Java Virtual Machine (JVM)

• Java is object-oriented, allowing for the creation of reusable code and modular programs

• Java is known for its robust standard library, which includes tools for networking, I/O, and more