40+ Java Full Stack Developer Interview Questions and Answers for Freshers

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

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

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.

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

Creating an Entity Class in Java

• Define class with @Entity annotation

• Add @Id annotation for primary key

• Include fields with appropriate data types

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.

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

The collection framework in Java provides a set of classes and interfaces for storing and manipulating groups of objects.

• 1. Interfaces: Core interfaces include List, Set, and Map. Example: List<String> names = new ArrayList<>();

• 2. Implementations: Various classes implement these interfaces. Example: HashSet, TreeSet for Set; HashMap, TreeMap for Map.

• 3. Algorithms: The framework provides algorithms for sorting and searching. Example: Collections.sort(list);

• 4. Iterators: Allows...read more

Exception handling in Java manages runtime errors, allowing the program to continue or terminate gracefully.

• Exceptions are events that disrupt the normal flow of execution in a program.

• Java uses try, catch, and finally blocks for exception handling.

• Example: try { int result = 10 / 0; } catch (ArithmeticException e) { System.out.println('Division by zero!'); }

• The 'finally' block executes regardless of whether an exception occurred, useful for cleanup.

• Custom exceptions can be c...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

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

Creating a REST API using Java Spring Boot involves setting up controllers, services, and repositories for data handling.

• 1. Set up a Spring Boot project using Spring Initializr with dependencies like 'Spring Web' and 'Spring Data JPA'.

• 2. Create a model class (e.g., 'User') with fields like 'id', 'name', and 'email'.

• 3. Implement a repository interface (e.g., 'UserRepository') extending JpaRepository for database operations.

• 4. Develop a service class (e.g., 'UserService') to ha...read more

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

The Map interface in Java represents a collection of key-value pairs, allowing efficient data retrieval based on keys.

• Maps store data in key-value pairs, e.g., Map<String, Integer> map = new HashMap<>();

• Common implementations include HashMap, TreeMap, and LinkedHashMap.

• Keys in a Map must be unique, while values can be duplicated.

• You can retrieve a value using its key, e.g., Integer value = map.get('key');

• Maps do not maintain any order of elements, except for TreeMap (sorted b...read more

Creating two beans in Java using Spring framework

• Use @Component annotation to define a bean

• Specify the bean name using @Component("beanName")

• Use @Autowired annotation to inject one bean into another

Transaction management in Hibernate ensures ACID properties for database operations.

• Hibernate provides built-in transaction management support through Session interface.

• Transactions can be managed programmatically using beginTransaction(), commit(), and rollback() methods.

• Hibernate also supports declarative transaction management using annotations like @Transactional.

• Transactions in Hibernate ensure Atomicity, Consistency, Isolation, and Durability for database operations.

Attached entities are actively managed by the persistence context, while detached entities are no longer actively managed.

• Attached entities are being managed by the persistence context and any changes made to them will be automatically synchronized with the database.

• Detached entities are not being managed by the persistence context and changes made to them will not be automatically synchronized with the database.

• Entities become detached when the persistence context is closed,...read more

Java is a versatile, object-oriented programming language used for building applications across various platforms.

• Platform Independence: Java applications can run on any device with a Java Virtual Machine (JVM). Example: Write once, run anywhere.

• Object-Oriented: Java supports concepts like inheritance, encapsulation, and polymorphism. Example: Creating classes and objects.

• Rich API: Java provides a comprehensive set of libraries for tasks like networking, I/O operations, and G...read more

A lambda expression is a concise way to represent an anonymous function in Java, enabling functional programming features.

• Syntax: (parameters) -> expression or (parameters) -> { statements; }

• Used primarily to implement functional interfaces.

• Example: (x, y) -> x + y is a lambda that adds two numbers.

• Can be used with Java's Stream API for operations like filter, map, and reduce.

• Enhances code readability and reduces boilerplate code.

Multithreading is a programming concept that allows concurrent execution of multiple threads within a single process.

• Improves application performance by utilizing CPU resources efficiently.

• Allows multiple tasks to run simultaneously, e.g., downloading files while processing data.

• Java provides built-in support for multithreading through the Thread class and Runnable interface.

• Synchronization is crucial to prevent data inconsistency when multiple threads access shared resources...read more

There are three types of autowiring in Spring: byType, byName, and constructor.

• byType: Spring looks for a bean of the same type and injects it.

• byName: Spring looks for a bean with the same name and injects it.

• constructor: Spring looks for a constructor and injects the arguments.

Filter a List using Streams in Java

• Use the filter() method to apply a predicate to each element in the stream

• Use collect() method to convert the stream back to a List

• Example: List<String> names = Arrays.asList("Alice", "Bob", "Charlie"); List<String> filteredNames = names.stream().filter(name -> name.startsWith("A")).collect(Collectors.toList());

Sort an Employee HashMap based on keys or values

• Use TreeMap to automatically sort by keys

• Use Comparator to sort by values

• Convert HashMap to List and then sort