Interview Questions on Java And Angular
Interview Questions on Java
1. What are the features of Java?
Java is a robust, secure, and platform-independent language that is simple, object-oriented, distributed, and dynamic.
2. What are the four principles of OOPS?
The four principles of OOPS are inheritance, encapsulation, polymorphism, and abstraction.
3. What is a class?
A class is a blueprint or template for creating objects that define the properties and methods of an object.
4. What is an object?
An object is an instance of a class that has properties and methods defined in the class.
5. What is a constructor?
A constructor is a special method that is used to create objects and initialize their properties.
6. What is inheritance?
Inheritance is a mechanism in which a new class is created by inheriting the properties and methods of an existing class.
7. What is abstraction?
Abstraction is the process of hiding the complexity of an object and only showing the essential features to the user.
8. What is an interface?
An interface is a collection of abstract methods and constants that are used to define a set of behaviors.
9. What is a memory leak?
A memory leak occurs when an application continues to allocate memory without releasing it, causing the system to run out of memory.
10. What is a thread in Java?
A thread is a lightweight process that allows multiple tasks to be executed concurrently within a single program.
11. What is synchronization in Java?
Synchronization is the process of controlling access to shared resources in a multi-threaded environment to avoid data inconsistency and deadlock.
12. What is a hash table in Java?
A hash table is a data structure that stores key-value pairs and provides fast access to the values based on their keys.
13. What is a map in Java?
A map is a collection that stores key-value pairs, where each key maps to a unique value.
14. What is a try-catch block in Java?
A try-catch block is used to handle exceptions in Java. The try block contains the code that may generate an exception, while the catch block handles the exception if it occurs.
15. What is the difference between forward() and sendRedirect() methods in Servlets?
The forward() method is used to forward the request to another resource on the server, while the sendRedirect() method is used to redirect the request to a different URL on the same or a different server.
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16. How do you handle exceptions in a Servlet?
You can handle exceptions in a Servlet by using the try-catch block and forwarding the request to an error page using the RequestDispatcher object.
17. What is the purpose of the ServletContext object in a Servlet?
The ServletContext object is used to provide access to the web application’s context, which includes information about the web application and its environment.
18. How do you retrieve parameters from a request in a Servlet?
You can retrieve parameters from a request in a Servlet by using the getParameter() method of the HttpServletRequest object.
19. What is a session in Servlets?
A session in Servlets is a mechanism that allows the server to maintain state between multiple requests from the same client. The HttpSession object is used to manage sessions in Servlets.
20. What is a Java framework?
A Java framework is a pre-written codebase that developers can use to build applications faster and more efficiently by providing a set of standard functionalities and patterns.
21. What are some popular Java frameworks?
Some popular Java frameworks include Spring, Hibernate, Struts, Play, JSF, Vaadin, and GWT.
22. What is Hibernate Framework?
Hibernate Framework is an open-source Java framework that provides a powerful object-relational mapping (ORM) solution for Java applications.
23. What is the difference between a library and a framework in Java?
A library is a collection of pre-written code that developers can use to perform specific tasks, while a framework is a complete solution that provides a set of standard functionalities and patterns.
24. What is the role of Maven in Java frameworks?
Maven is a build automation tool that helps in the management and building of Java projects. It is commonly used in Java frameworks to manage dependencies and build the project.
25. What is the role of ORM in Java frameworks?
ORM (Object-Relational Mapping) is a technique used in Java frameworks to map database tables to Java objects, and vice versa. It helps in the efficient management of data and provides a high level of abstraction.
26. What is JSX in ReactJS?
27. What is the Virtual DOM in ReactJS?
The Virtual DOM is a lightweight copy of the real DOM that ReactJS uses to efficiently render changes to the UI without reloading the entire page.
28. What is the role of the render() method in ReactJS?
The render() method is used to render the UI of a component. It returns a tree of React elements that represent the UI.
29. What is the role of the componentDidMount() method in ReactJS?
The componentDidMount() method is a lifecycle method that is called once a component is mounted. It is used to perform initialization tasks like fetching data from APIs.
Interview Questions On Angular
30. What is Angular?
Angular is an open-source, front-end web application framework developed by Google for building dynamic web applications.
31. What is the difference between AngularJS and Angular?
AngularJS is an earlier version of Angular that uses a different architecture and syntax. Angular, on the other hand, is a complete rewrite of AngularJS with a different architecture and syntax.
32. What is a directive in Angular?
A directive is a way to extend HTML with custom attributes and behaviors. It can be used to create reusable components, apply styles, and manipulate the DOM.
33. What is a service in Angular?
A service is a class in Angular that provides functionality that can be shared across multiple components. It can be used to fetch data from APIs, manipulate data, and perform other tasks.
34. What is dependency injection in Angular?
Dependency injection is a design pattern used in Angular to manage the dependencies of components and services. It allows for better modularity and easier testing.
35. What is the role of the ngOnInit() method in Angular?
The ngOnInit() method is a lifecycle hook in Angular that is called once a component is initialized. It is used to perform initialization tasks like fetching data from APIs.
36. What is a module in Angular?
A module is a way to organize an Angular application into cohesive blocks of functionality. It consists of a collection of components, services, directives, and other related codes.
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37. What are some advantages of using Angular?
Some advantages of using Angular include a powerful set of features, a large community with plenty of resources and support, improved performance, better scalability, and a modular architecture.
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39. What is NPM?
NPM (Node Package Manager) is a package manager for Node.js that allows developers to install, manage, and share packages of code.
40. What is a module in Node.js?
A module is a self-contained piece of code that can be reused across multiple projects. In Node.js, modules are typically organized into separate files and can be imported and used in other files using the “require” function.
41. What is the “event loop” in Node.js?
The event loop is a fundamental concept in Node.js that allows it to handle multiple concurrent requests efficiently. It is responsible for managing the execution of asynchronous operations and ensuring that the application remains responsive.
42. What is the role of the “fs” module in Node.js?
The “fs” module is a built-in module in Node.js that provides an interface for working with the file system. It allows developers to read and write files, create and delete directories, and perform other file-related operations.
43. What are some advantages of using Node.js?
Some advantages of using Node.js include its ability to handle large volumes of data and concurrent requests, its high scalability and performance, its large and active community, and its support for asynchronous programming.
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