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 Q241. Do you prefer using var args ?Core Java
Ans. Though var args are used rarely but they are pretty useful if a method is expected to receive variable number of arguments. For example - it's pretty useful for the main method as the caller has the flexibility to provide arguments in infinite ways.It provides a convenience and flexibility to the caller.

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   Like         Discuss         Correct / Improve     var args  methods  method declarations  functions


 Q242. What is meant by "Vector is synchronized and ArrayList isn't " ?Core Java
Ans. It means that only 1 thread can access have access to Vector at a time and no parallel access is allowed whereas Array List allows parallel access by multiple threads.

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   Like         Discuss         Correct / Improve     vectors  arraylist  collections  list  synchronization  synchronized


 Q243. How can we ensure thread safety in static method ?Core Java
Ans. By using synchronized static method or synchronized block

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   Like         Discuss         Correct / Improve     threads  synchronization  static methods     Asked in 2 Companies      intermediate


 Q244. What is abstraction ?Design
Ans. Abstraction is a process of hiding the implementation details and describing only the functionality to the user.

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   Like         Discuss         Correct / Improve     bstraction  oops concepts  oops principle     Asked in 22 Companies


 Q245. Which collection stores element in insertion order ?Core Java
Ans. LinkedList maintains the insertion order in collection.

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   Like         Discuss         Correct / Improve     collections     Asked in 1 Companies


 Q246. What are the reasons to choose between reserved and on demand instances ?Server
Ans. In terms of compute options and configurations, Reserved Instances and On Demand instances are the same. The only difference between the two is that a Reserved Instance is one you rent (reserved) for a fixed duration, and in return you receive a discount on the base price of an On Demand instance.

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   Like         Discuss         Correct / Improve     aws  aws ec2  aws computing  amazon cloud computing  amazon ec2  production support  Google Cloud Platform (GCP)


 Q247. Describe structure of a Web application.architecture
Ans. WEB APP |WEB-INF - META-INF | | | META-INF.MF | lib - WEB.xml - Classes

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   Like         Discuss         Correct / Improve     web application     Asked in 3 Companies      intermediate        frequent


  Q248. What are the types of authentication used in Web services ?Web Service
Ans. Encrypted User Name / Password
Encrypted Password within Cookie
Encrypted Tokens
IP
Client Certificates
Oauth

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   Like         Discuss         Correct / Improve     authentication  security  web service     Asked in 12 Companies      basic        frequent


 Q249. Does use of Final class enforces composition over Inheritance in Java ? Core Java
Ans. Yes, to a certain extent. But the objective for Final class could be beyond just enforcing composition as certain classes might have been created without inheritance or composition in mind.

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   Like         Discuss         Correct / Improve     final class   composition  object oriented programming (oops)  oops concepts  inheritance  object oriented programming (oops)  oops concepts  composition  object oriented programming (oops)  oops concepts vs inheritance  object oriented programming (oops)  oops concepts      expert


 Q250. Explain OAuth.Authentication
Ans. OAuth is an open-standard authorization protocol or framework that describes how unrelated servers and services can safely allow authenticated access to their assets without actually sharing the initial, related, single logon credential. Like using Google or Facebook to login to something.

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   Like         Discuss         Correct / Improve          Asked in 17 Companies


 Q251. Between Encrypted Password authentication and IP Authentication , which one would you prefer and why ?Authentication
Ans. IP authentication is very restrictive, if IP changes for some reason then getting the new IP white listed on the server firewall could run your day pretty long. I would prefer encrypted password authentication cause it is not affected by IP changes and not limited to a white listed IP, I could use any different machine and get through authentication without any hassle.

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   Like         Discuss         Correct / Improve     ip authentication   password authentication        frequent


 Q252. Can we declare an array without assigning the size of an array? Core Java
Ans. No, It will throw compile time error saying "must provide either dimension expressions or an array initializer"

Alternatively we can provide array initializer like

String[] strArray = new String[]{"Buggy","Bread"};

which will initialize it to size 2 with values as "Buggy" and "Bread"


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   Like         Discuss         Correct / Improve     arrays  array initialization


 Q253. Difference between StoreModule.forRoot() and StoreModule.forFeature() ?NgRx
Ans. forFeature is used for lazily registering reducers with the module.

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   Like         Discuss         Correct / Improve     ngrx    angular   angular ngrx integration  ngrx store


 Q254. How to avoid cloning, serialization in the singleton class ?Design
Ans. For Cloning-exception,For deserialization-read.resolve()

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   Like         Discuss         Correct / Improve     singleton  cloneable  serializable  serialization  cloning     Asked in 1 Companies


 Q255. Which AWS computing service provides IAAS, PAAS , Containerization and Serverless ?Amazon Web Services (AWS)
Ans. EC2 is IAAS
Elastic Beanstalk is PAAS
EKS is Containerization service
Lambda is Serverless

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   Like         Discuss         Correct / Improve     IAAS   PAAS    Containerization  Serverless


 Q256. What are different ways a user can be authenticated other than username / password ?Authentication
Ans. IP Authentication
IP Range Authentication
Certificates
Authentication Cards

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 Q257. Why would a cloud customer use resources in multiple regions and zones ?Cloud Computing
Ans. 1. Fault Tolerance
2. Better Access by bringing the application closer to the users.

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   Like         Discuss         Correct / Improve     Google Cloud Computing (GCP)  Amazon Web Services (AWS)  Availability Zones  Regions and Zones  Infrastructure


 Q258. Have you ever heard about csrf attacks ?Security
Ans. Yes, Cross-Site Request Forgery (CSRF) is an attack that forces an end user to execute unwanted actions on a web application in which they're currently authenticated.

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   Like         Discuss         Correct / Improve     csrf attack  Cross-Site Request Forgery (CSRF)     Asked in 16 Companies


 Q259. What is concurrent interface ?Core Java
Ans. ConcurrentMap is an interface and it is a member of the Java Collections Framework. It represents a Map that is capable of handling concurrent access to it without affecting the consistency of entries in a map. ConcurrentMap interface present in java.util.concurrent package.

HashMap operations are not synchronized, while Hashtable provides synchronization. Though Hashtable is thread-safe, it is not very efficient. To solve this issue, the Java Collections Framework introduced ConcurrentMap in Java 1.5.

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   Like         Discuss         Correct / Improve     Concurrent Interface   java.util.concurrent   Java 8 Concurrency   java concurrency   java 8     Asked in 1 Companies


  Q260. What is a cookie ?Java EE
Ans. A cookie is a small piece of text stored on a user's computer by the browser for a specific domain. Commonly used for authentication, storing site preferences, and server session identification.

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   Like         Discuss         Correct / Improve     cookie   javascript   web application   session management   browser   j2ee     Asked in 16 Companies      basic        frequent


 Q261. What is servlet Chaining ?Java EE
Ans. Multiple servlets serving the request in chain.

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   Like         Discuss         Correct / Improve     java   web application   servlets     Asked in 1 Companies        rare


Very frequently asked. Usually asked in this format or as difference with interfaces / concrete classes.
  Q262. What is an abstract class ?Core Java
Ans. Abstract class is the class that is not supposed to be instantiated. The purpose of the class to only have extension to the derived class.

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   Like         Discuss         Correct / Improve     abstract class     Asked in 6 Companies      basic        frequent


 Q263. Which interface does java.util.Hashtable implement?Core Java
Ans. Java.util.Map

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   Like         Discuss         Correct / Improve     java   collections   hashtable   map      basic        rare


Frequently asked.
  Q264. What is an Iterator?Core Java
Ans. Iterator is an interface that provides methods to iterate over any Collection.

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   Like         Discuss         Correct / Improve     java   collections   iterator     Asked in 11 Companies      basic        frequent


 Q265. Which interface provides the capability to store objects using a key-value pair?Core Java
Ans. java.util.map

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   Like         Discuss         Correct / Improve     java   collections   map      basic        frequent


 Q266. What are transient variables in java?Core Java
Ans. Transient variables are variable that cannot be serialized.

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   Like         Discuss         Correct / Improve     java   serialization   transient     Asked in 15 Companies      intermediate        rare


 Q267. How does a try statement determine which catch clause should be used to handle an exception?Core Java
Ans. When an exception is thrown within the body of a try statement, the catch clauses of the try statement are examined in the order in which they appear. The first catch clause that is capable of handling the exception is executed. The remaining catch clauses are ignored.

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   Like         Discuss         Correct / Improve     java   exceptions   exception handling   try   catch      basic        frequent


 Q268. what is content negotiation?
Ans. Suppose we want to visit a site for any information, information can be represented in different languages like English,German or may be other and their format for presentation can also differ from HTML to PDF or may be Plain text. In this case when an client makes an HTTP request to a server, client can also specify the media types here. Client can specify what it can accept back from host and on the basis of availability the host will return to the client. This is called content negotiation because client and server negotiated on the language and format of the content to be shared.

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   Like         Discuss         Correct / Improve     j2ee   internet   content negotiation   http   architecture


  Q269. Explain static blocks in Java ?Core Java
Ans. A static initialization block is a normal block of code enclosed in braces, { }, and preceded by the static keyword. Here is an example:

static {
// whatever code is needed for initialization goes here
}

A class can have any number of static initialization blocks, and they can appear anywhere in the class body. The runtime system guarantees that static initialization blocks are called in the order that they appear in the source code.

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   Like         Discuss         Correct / Improve     java   oops   static   static block     Asked in 16 Companies      basic        frequent


 Q270. Explain Annotations ?
Ans. Annotations, a form of metadata, provide data about a program that is not part of the program itself. Annotations have no direct effect on the operation of the code they annotate. Annotations have a number of uses, among them:
• Information for the compiler — Annotations can be used by the compiler to detect errors or suppress warnings.
• Compile-time and deployment-time processing — Software tools can process annotation information to generate code, XML files, and so forth.
• Runtime processing — Some annotations are available to be examined at runtime.

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   Like         Discuss         Correct / Improve     java   annotations      basic        frequent


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