Interview Questions and Answers for 'T' | Search Interview Question

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Q481. What are the reasons to choose between reserved and on demand instances ?

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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Q482. Find different combination of given String and trace the output

Core Java

Ans. private void permutation(String prefix, String sufix)
{
int ln = sufix.length();
if(ln == 0) {
System.out.println(prefix);
} else {
IntStream.range(0, ln).forEach(i->permutation(prefix sufix.charAt(i), sufix.substring(0,i) sufix.substring(i 1, ln)));
}
}

call:permutation("", "abcdef");

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Q483. Can you explain the integration between API Gateway and Lambda if we wish to develop services using these tools.

Amazon Web Services (AWS)

Ans. We can create API gateway and give the name of lambda function in order to be linked with lambda function, deploy the API and whenever request will be made from API it will directly be linked to lambda function to perform further process.

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Q484. Why do we need to specify import statement ? Don't you think Java could have been designed in such a way to automatically import everything that's in the class path ?

Core Java

Ans. Java could design it in such a manner but would result in ambiguity if there are multiple files with the same name. The only way to get over it to show the message when you use any such class to provide explicit import with the package prefix. The other problem could be that Java might have to change the early import to Late import and check what's being used to decide what needs to be imported as otherwise you will see errors regarding the ambiguous imports with duplicate file name.

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Q485. Which of the OOP's feature is most important ?

Core Java

Ans. Encapsulation facilitate hiding and restricted access and hence more of a security feature. Encapsulation is definitely a great feature as when applications expand criss cross communication between objects / modules could lead to blunders.

Inheritance facilitates code reuse.

Polymorphism comprise of method overloaded ( which to me is negligible usage ) and method overriding. Method overriding is of great usage as it facilitates concept of interfaces and plugin development.

So it’s Security / Organization vs

Code Reuse / Support for other features like overriding vs

Contracts / Plugin Development facilitating the creation of frameworks / libraries.

Which is more important may vary from application to application , its scale , its use , its sensitivity etc.

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Q486. Can we have a private default method ?

Core Java

Ans. No. The whole idea of default method is to provide a default definition in case the implementing class intend to provide definition for only some of the methods. Making any of the interface method private would restrict it from being implemented by the implementing class. So default method is an option to provide implementation and not restricting a new definition.

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Q487. Find Fibonacci first n numbers using recursion ?

Core Java

Ans. public int fibonacci(int n) {
if(n == 0)
return 0;
else
if(n == 1)
return 1;
else
return fibonacci(n - 1) fibonacci(n - 2);
}

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Q488. What is the difference between Observer and Observable ?

RxJava

Ans. Observable is emiting data and Observer is subscribing to catch the data

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Q489. Write code to redo and undo without using system functions ?

Design

^{This question was recently asked at 'Aloha Technologies'.This question is still unanswered. Can you please provide an answer.}

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Q490. What development process / methodology are you using ? Are you using agile ?

General

^{This question was recently asked at 'Spillman Technologies'.This question is still unanswered. Can you please provide an answer.}

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Q491. Can we have multiple inheritance in java using abstract class ?

Core Java

Ans. No

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Q492. Describe structure of a Web application.

architecture

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Q493. 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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Q494. 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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Q495. What could be the reasons for restricting inheritance using final class ?

Core Java

Ans. 1. Enforcing composition over inheritance
2. Restricting overriding of certain methods
3. Final methods are faster than regular instance methods
4. Enforcing Immutability

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Q496. 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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Q497. 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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Q498. Difference between Arrays and ArrayList ?

Core Java

Ans. Both Arrays and ArrayLists are used to store elements. Elements can be either primitives or objects in case of Arrays, but only objects can be stored in Arraylist. Array is a fixed length data structure while arraylist is variable length collection class. Once created, you cannot change the size of the arrays, but arraylists can dynamically resize itself when needed.Another notable difference between Arrays and Arrayslist is that arary is part of core java programming and array list is part of collection classes

Sample Code for arrays arraylist

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Q499. 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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Q500. What is the difference between log4j and java logging api.

Log4j

Ans. log4j is by apache while java logging api is given by sun. log4j is more powerful,extensible and simple to use than java logging api.

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Q501. Difference between StoreModule.forRoot() and StoreModule.forFeature() ?

NgRx

Ans. forFeature is used for lazily registering reducers with the module.

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Q502. What would you do if you see an error thrown by a lambda function as "Access Denied" while doing something with S3 ?

Amazon Web Services (AWS)

Ans. Just like people , AWS resources too have execution roles or permissions. Seems like in such a situation Lambda function may not have sufficient privileges to perform operations on S3. For example - The execution role of Lambda may just have read permissions on S3 and we may be trying to perform PutObject operation.

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Q503. What will happen if there are no interfaces in Java ?

Core Java

Ans. Abstract classes can take care of that to a certain extent. Though they are little heavier than Interfaces but An abstract class with all abstract methods and no instance variables will be able to help with everything that currently an interface does.

The only problem is that a class can only extend one class whereas it can implements multiple interfaces and that is the reason Interfaces were introduced in Java, i.e to get over the problem of multiple inheritance.

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Q504. How to avoid cloning, serialization in the singleton class ?

Design

Ans. For Cloning-exception,For deserialization-read.resolve()

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Q505. What is AWS Storage Gateway?

Amazon Web Services (AWS)

Ans. It's an on premise virtual appliance that can be used as cache to store s3 locally at customer site.

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Q506. What are the drawbacks of using Spot EC2 instances ?

Amazon Web Services (AWS)

Ans. You cannot reserve the time slot and they can be made to use whenever they are available.

AWS can Terminate the EC2 instance on their own even if it's in use.

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Q507. What is the use case for AWS Gateway cached , stored and VTL ?

Amazon Web Services (AWS)

Ans. AWS Cached - Low Availability than AWS Stored, Lower cost than AWS Stored

AWS Stored - High Availability, High Local Storage Cost

AWS VTL - S3 Used as Back up only.

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Q508. What are the things to consider while provisioning computing in AWS ?

Amazon Web Services (AWS)

Ans. Service ( EC2, Lambda etc )
AMI ( Operating System and Softwares )
Instance Type ( T,M, R etc )
EBS ( Volume Type , Size )
Price Class ( OnDemand, Dedicated etc )

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Q509. How have you configured Security Groups ?

Amazon Web Services (AWS)

Ans. AWS console >> security groups >> Create security group >> Configure security group bases on Network requirement of EC2 instance

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Q510. What is the purpose of EC2 Health check ?

Amazon Web Services (AWS)

Ans. We can use this check for variety of things -

1. Monitoring the status / Alarms in case it's down
2. Regulating traffic to healthy instances only through Load Balancer

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