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Q61. Do you think it's a good practice to keep passwords in config files ?

Solution

Ans. We can keep them in config as encrypted values.

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Q62. Can we keep application configuration at different places and what could be the consideration for choosing multiple places for doing so ?

Design

Ans. Yes an application can have configuration stored at multiple places. Factors that could facilitate such a design could be

1. Type of config information - We may have a case to store confidential information differently than other regular config value

2. Environment - We may like to have a base config ( defined in application package ) and then a different override mechanism in different environments.

3. Centralization - Sometime some configs need to be shared across application and hence centralized.

4. Testing - Testing against config may not be possible in some enviornments in certain cases and hence additional config store might be kept for testing purpose only.

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Q63. How would you test a Twitter application ?

Testing

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

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Q64. why is "".equals(str); safer than str.equals("")?

Core Java

Ans. str.equals("") this statement will throw NullPointerException if str is null where as "".equals(str) works fine even if str is null

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Q65. Design an in memory object oriented system for a Car manufacturing Company ?

Design

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Q66. If you are asked to develop a financial system, how would you make sure that there are proper checks , balances and audits ?

Solution

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Q67. There is a server which is 90% full, I need to increase the space. How can I do it ?

Server

Ans. Firstly ,we have removed old backup data from server after that we are checking which user consume high memory through df command.

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Q68. What are inline functions ?

Programming Language

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Q69. What are inline functions ? Do we have inline functions in Java ?

Core Java

Ans. Inline functions , just like C++ Macros is an optimized technique used by compiler to reduce the execution time. If the function is working on pre identified values ( which aren't resolved at runtime ), the function can execute the method and evaluate the outcome at compile time only instead of making a function call at runtime.

In Java, the optimizations are usually done at the runtime or JVM level. At runtime, the JVM perform some analysis to determine which methods to inline. Java compiler would never inline any method and there is no way in java for the developer to explicitly define inlining of methods as it's take intrinsically care of during runtime only.

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Q70. 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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Q71. Difference between Containerization and Serverless ?

Infrastructure

Ans. Following are key differences between containers and serverless:

Supported host environments: Containers can run on any modern Linux server, as well as certain versions of Windows. In contrast, serverless runs on specific host platforms, most of which are based in the public cloud (like AWS Lambda or Azure Functions).

Self-servicing ability. For the reasons just noted, in most cases, serverless functions require you to use a public cloud. (There are on-premises serverless frameworks, like Fn, but these are not yet widely used.) With containers, you can set up your own on-premises host environment, or use a public cloud service like ECS.

Cost. Because serverless environments are hosted in the cloud, you have to pay to use them. In contrast, you can set up a container environment yourself using open source code for free (although you’ll still have management costs, of course).

Supported languages. You can containerize an application written in any type of language as long as the host server supports the language. Serverless frameworks are different; they support a limited number of languages. The details of supported serverless language vary from serverless platform to platform.

Statefulness. Most serverless platforms are designed to support stateless workloads. (Some serverless providers offer limited support for stateful services; cf. Durable Functions on Azure.) Although you can connect to external storage services (like S3 on AWS) from within serverless platforms, the functions themselves cannot be stateful. Containers present their own persistent storage challenges, but creating stateful containerized apps is certainly possible.

Availability. Serverless functions are designed to run for a short period—usually, a few hundred seconds—before they shut down. Containers can run for as long as you need.

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Q72. Difference between List and ArrayList ?

Core Java

Ans. List is an interface whereas ArrayList is an implementation of List.

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Q73. Which is the default AWS Region ?

Amazon Web Services (AWS)

Ans. US-EAST-1

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Q74. How can EBS Volumes be backed up ?

Amazon Web Services (AWS)

Ans. Through Snapshots

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Q75. What is the need of S3 Transitioning ?

Amazon Web Services (AWS)

Ans. Saving Cost by either expiring objects or moving to low cost storage.

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Q76. What is the use case of S3 Cross Region replication ?

Amazon Web Services (AWS)

Ans. Disaster Recovery and availability

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Q77. If you override hashcode to always return true, how a hash based collection will behave?

Core Java

Ans. At that bucket, it will form a linked list depending on what equals method evaluates for that object.

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Q78. Which AWS services would you use if you have find a cheapest solution for an analytics application ?

Amazon Web Services (AWS)

Ans. Computation

Spot Price Plan
F1 or P3 Instance Type
Cold Hdd (SCI ) EBS Volume

Storage

S3-IA

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Q79. write a program for 4 digit otp generation?

Design

Ans. import java.util.Random;

public class OTPGenerator {
public static void main(String[] args) {
int otpLength = 4;
String otp = generateOTP(otpLength);
System.out.println("Generated OTP: " otp);
}

private static String generateOTP(int length) {
StringBuilder otp = new StringBuilder();
Random random = new Random();

for (int i = 0; i < length; i ) {
int digit = random.nextInt(10);
otp.append(digit);
}

return otp.toString();
}
}

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Q80. What are the advantage of having Edge Locations ?

Amazon Web Services (AWS)

Ans. It saves Network traffic and facilitates faster delivery by hosting bulk media and cached data near to client.

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Q81. Which AWS service is provided by Edge location ?

Amazon Web Services (AWS)

Ans. As Edge location only host cached content, Amazon CDN service or CloudFront is provided on these locations.

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Q82. Difference between Region , Availability zone and Edge Locations ?

Amazon Web Services (AWS)

Ans. A Region is a Geographical entity like US-East , US-West etc. Each Region may have multiple availability zones where each zone comprise of 1 or more Data Center located with each other.

Edge Locations are the sites that hosts cached content for faster delivery and for saving network traffic as they feed content from sites that are local or near to consumption.

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Q83. Which region is the latest and most popular in AWS ? What are the advantages and disadvantages of using this region ?

Amazon Web Services (AWS)

Ans. US-East Virginia

This is the oldest and most popular region. All new features are rolled first in this region and hence they are first available there. The downside is that because of experimentation with new services, unavailability time is quite high.

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Q84. How did you use Spring in your project ? Which Spring annotations have you used in your project ?

Spring

Ans. @RequestMappping

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Q85. Difference between AWS Cloud Formation and AWS AMI ?

Amazon Web Services (AWS)

Ans. AMI is an Amazon Machine Image. It contains the configuration to enable to boot up an EC2 instance with said configuration whereas Cloud formation is a templating language that allows to describe how to build a VPC and also allows you to create AWS services

AMI is templating specific to instances whereas the scope of CloudFormation templating is much bigger. CloudFormation could use AMI for launching instances along with other services.

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Q86. Can we serialize objects with only private variables in Java ?

Core Java

Ans. It depends on how we are serializing. The Serialization API doesn't worry about private variables and convert it into binary representation.

If we are using a library to map it to JSON / XML using XML Mappers, it may create trouble.

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Q87. Pascal Triangle Program

Ans. package snippet;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Pascal {
   public static void main(String[] args) {

      System.out.println(generatePascalTriangle(5));

   }

   static Map> generatePascalTriangle(int size) {
      Map> triangle = new HashMap<>();

      triangle.put(0, Arrays.asList(1));
      triangle.put(1, Arrays.asList(1, 1));

      for (int i = 2; i <= size; i ) {
         List coeffListForI = new ArrayList<>();
         List coeffListForI_1 = triangle.get(i - 1);
         coeffListForI.add(1);
         for (int j = 0; j <= coeffListForI_1.size() - 2; j ) {
            coeffListForI.add(coeffListForI_1.get(j) coeffListForI_1.get(j 1));
         }
         coeffListForI.add(1);
         triangle.put(i, coeffListForI);
      }

      return triangle;
   }
}

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Q88. What is the cost of using Cloud Formation ?

Amazon Web Services (AWS)

Ans. Cloud Formation does not have any additional cost but you are charged for the underlying resources it builds.

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Q89. Explain different inheritance mapping strategies with JPA / Hibernate.

Hibernate

Ans. table per hierarchy
table per concrete class
table per sub class

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Q90. How to avoid cloning, serialization in the singleton class ?

Design

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

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