Wipro Full Stack Interview Questions and Answers

1. What are keys in React lists?

The “key” prop is a special attribute that needs to be included when creating lists of elements. The key serves as a unique identifier for each item in the list.

2. What is @Component in Angular?

@Component: This decorator is used to define a component. It includes a template, styles, and logic to control a view. Components are the main building blocks of an Angular application.

import { Component } from @angular/core @Component({ selector: app-example template: <h1>Hello, World!</h1> styles: [h1 { color: blue; }] }) export class ExampleComponent {}

3. What is synchronization in Java?

Synchronization is a mechanism to control the access of multiple threads to shared resources to prevent data inconsistency.

4. What are the different types of error handling in JavaScript?

try…catch blocks
throw statements
custom error objects.

5. What is Spring Boot Starter? Give examples for Spring Boot starters.

Spring Boot Starter is a set of convenient dependency descriptors. It can be included in the applications to quickly get up and running with various Spring technologies.

Examples of Common Spring Boot Starters:

1. spring-boot-starter-web

This starter is used for building web applications using Spring MVC.

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency>

2. spring-boot-starter-data-jpa

This starter helps in setting up JPA repositories with Hibernate as the default JPA implementation.

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency>

6. How do you handle cross-origin resource sharing (CORS) in a Spring Boot application?

Using @CrossOrigin Annotation

The @CrossOrigin annotation can be applied to controllers or specific handler methods to allow CORS on certain endpoints.

1. Enable CORS for a Controller:

import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController @CrossOrigin(origins = http:) { @GetMapping(/example) public String exampleEndpoint() { return CORS Example } }

2. Enable CORS for a Specific Endpoint:

import org.springframework.web.bind.annotation.CrossOrigin; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; @RestController public class ExampleController { @CrossOrigin(origins = http://example.com) // Allow only the specified origin @GetMapping(“/example”) public String exampleEndpoint() { return CORS Example } }

7. Explain the concept of inheritance in object-oriented programming.

Inheritance is a mechanism where a new class (child) derives properties and behaviors from an existing class (parent), promoting code reuse.

8. What are the different types of CSS selectors?

Element, Class, ID, Attribute, Pseudo-class, and Pseudo-element selectors.

9. What are the different types of joins in SQL?

INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL OUTER JOIN, CROSS JOIN.

10. Explain ACID properties in databases.

Atomicity, Consistency, Isolation, Durability

To ensure reliable transactions in databases.

11. What is the event loop in JavaScript?

The event loop is responsible for executing the code, collecting and processing events, and executing queued sub-tasks.

12. What are let, const, and var?

var is function-scoped or globally-scoped, let and const are block-scoped. const cannot be reassigned.

13. What is the difference between JDK, JRE, and JVM?

JDK (Java Development Kit) includes JRE and development tools.
JRE (Java Runtime Environment) provides libraries and JVM for running applications.
JVM (Java Virtual Machine) executes Java bytecode.

14. Explain Angular Lifecycle Hooks.

Angular lifecycle hooks are a set of methods that are invoked at different stages of a component’s lifecycle. These hooks allow developers to tap into key moments of a component’s lifecycle, such as when it is created, initialized, changed, or destroyed.

15. List out the Angular Lifecycle Hooks.

ngOnInit: called once, after the component’s constructor has been called and after the first ngOnChanges.

ngOnChanges: Called when an input property changes.

ngDoCheck: Called during every change detection run.

ngAfterContentInit: Called after content (ng-content) has been projected into view.

ngAfterContentChecked:Called after every check of projected content.

ngAfterViewInit: Called after the component’s view (and child views) has been initialized.

ngAfterViewChecked: Called after every check of the component’s view (and child views).

ngOnDestroy: Called just before the component is destroyed.

16. What are generators in Python?

Generators in Python are a type of iterable, like lists or tuples. Unlike lists, they generate values on the fly and do not store them in memory. This makes generators highly efficient for handling large datasets.

Basic Generator:

def simple_generator(): yield 1 yield 2 yield 3 gen = simple_generator() for value in gen: print(value) Output: 1 2 3

17. Illustrate Decorator with Arguments in Python

def repeat(n): def decorator(func): def wrapper(*args, **kwargs): for _ in range(n): func(*args, **kwargs) return wrapper return decorator @repeat(3) def say_hello(name): print(f;Hello, {n;) say_hello(Credo;) Output: Hello, Credo! Hello, Credo! Hello, Credo!

18. What are closures in JavaScript and how are they useful?

A closure in JavaScript is a function that retains access to its lexical scope, even when the function is executed outside that scope. Closures allow for the creation of private variables and can be used to create factory functions or modules.

19. What is the difference between call, apply, and bind in JavaScript?

Call, apply, and bind are methods in JavaScript used to change the context (this) of a function.

call: Invokes the function immediately with a given this value and arguments provided individually.
apply: Invokes a function with a given this and arguments as an array.
bind: Returns a new function with a given this and optional pre-set arguments.

20. Differentiate generators from Regular Functions

Memory Efficiency: Generators yield items one at a time and only keep track of the current state, unlike lists that store all elements in memory.
Statefulness: Generators remember their state between iterations, enabling the function to resume execution right after the last yield statement.
Lazy Evaluation: Values are computed on-the-fly, which is useful for generating large sequences.

21. What are useMemo and useCallback?

React hooks enable functional components to use state and lifecycle features. useMemo and useCallback optimize performance. It prevents unnecessary recalculations and re-renders.

useMemo: Memoizes a computed value.

const memoizedValue = useMemo(() => computeExpensiveValue(a, b), [a, b]);
useCallback: Memorizes a function.

const memoizedCallback = useCallback(() => { doSomething(a, b); }, [a, b]);

22. What is the Context API and how can you use it to manage state in a React application?

The Context API in React allows sharing state across components without prop drilling. It’s useful for global states like user authentication, themes, and settings.

23. What is the difference between ArrayList and LinkedList in Java?

ArrayList: It uses a dynamic array to store elements. It provides fast random access (O(1)) but slower insertions and deletions (O(n)) as elements need to be shifted.

LinkedList: It uses a doubly linked list to store elements. It provides faster insertions and deletions (O(1)) but slower random access (O(n)).

24. What are the differences between HashMap and TreeMap in Java?

HashMap: Implements the Map interface using a hash table. It allows null keys and values and does not maintain any order of the elements.

TreeMap: Implements the NavigableMap interface using a red-black tree. It does not allow null keys but allows null values.

25. What is the significance of the final keyword in Java?

The final keyword can be applied to variables, methods, and classes, each with different implications:

Final Variable: Once assigned, its value cannot be changed (it becomes a constant).
Final Method: The method cannot be overridden by subclasses.
Final Class: The class cannot be subclassed.

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Wipro Full Stack Interview Questions and Answers