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Q751. Is this code valid

String[] strArray = new String[2];
strArray.length = 5;

Ans. It will give compile time error saying "The final field array.length cannot be assigned"

Arrays once initialized cannot be resized.

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Q752. Will this give compile time error ?

Object[] strArray = new String[2];
strArray[0] = 5;

Core Java

Ans. No. But It will throw ArrayStoreException at runtime.

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Q753. What is TypeCasting ?

Core Java

Ans. Assigning a value of one type to a variable of another type is known as Type Casting.

Example :

int x = 10;
byte y = (byte)x;

In Java, type casting is classified into two types, Widening Casting(Implicit) widening-type-conversion and Narrowing Casting (Explicitly done) narrowing-type-conversion.

Widening or Automatic type converion - Automatic Type casting take place when,the two types are compatible and the target type is larger than the source type

Example :

public class Test {
public static void main(String[] args) {
int i = 100;
long l = i; //no explicit type casting required
float f = l;//no explicit type casting required
System.out.println("Int value " i);
System.out.println("Long value " l);
System.out.println("Float value " f);
}
}

Narrowing or Explicit type conversion - When you are assigning a larger type value to a variable of smaller type, then you need to perform explicit type casting.

Example :

public class Test{
public static void main(String[] args) {
double d = 100.04;
long l = (long)d; //explicit type casting required
int i = (int)l;//explicit type casting required
System.out.println("Double value " d);
System.out.println("Long value " l);
System.out.println("Int value " i);
}
}

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Q754. What are basic functions of OOPS ?

Core Java

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Q755. Where to use interface and abstract class ?

Core Java

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Q756. Does Java SE has Immutable collections ?

Core Java

Ans. Yes wef from Java 9

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Q757. Is java fully platform independent ?

Core Java

Ans. yes, Java is a class-based and object-oriented programming language. It is a platform-independent language i.e. the compiled code can be run on any java supporting platform. It runs on the logic of “Write once, run anywhere”.

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Q758. Which s/w is used for adhar card verification for amount transfer?

Ans. The Aadhaar enabled Payment System or AePS

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Q759. Isnt the use of HashTable and ConcurrentHashMap the same, i.e providing synchronized map collection ?

Core Java

Ans. Both provide the thread safety but the actual difference come when talk about performance. CHM gives best performance when no of writer threads are less in number.

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Q760. How can we schedule Lambda function to run daily ?

Amazon Web Services (AWS)

Ans. We can schedule that through CloudWatch.

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Q761. What is the difference between try-catch and @ExceptionHandler in Java/Spring Boot?

Spring Boot

Ans. ExceptionHandler is Used to handle at Method level

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Q762. Difference between indexing and partioning

Database

Ans. Creating an index creates a separate table. ... Indexes are used to speed the search of data within tables. Partitions provide segregation of the data at the hdfs level, creating sub-directories for each partition. Partitioning allows the number of files read and amount of data searched in a query to be limited

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Q763. Explain Hibernate caching mechanism

Hibernate

Ans. Every fresh session having its own cache memory, Caching is a mechanism for storing the loaded objects into cache memory. The advantage of cache mechanism is, whenever again we want to load the same object from the database then instead of hitting the database once again, it loads from the local cache memory only, so that the no. of round trips between an application and a database server got decreased. It means caching mechanism increases the performance of the application.

In hibernate we have two levels of caching

First Level Cache [ or ] Session Cache
Second Level Cache [ or ] Session Factory Cache [ or ] JVM Level Cache

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Q764. Does it make sense to mock integration calls during stress / load test ?

Testing

Ans. No, its usually not done.

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Q765. What are the 7 OSI LAYERS ?

Networking

Ans. Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 - Physical

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Q766. What will happen if there are no collections in java ?

Core Java

Ans. Collections in Java is nothing but a library implementation for data structures and algorithm. If it's not available , we might have to include some other library or provide our own implementation.

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Q767. 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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Q768. 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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Q769. 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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Q770. How did you use Spring in your project ? Which Spring annotations have you used in your project ?

Spring

Ans. @RequestMappping

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Q771. 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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Q772. 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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Q773. 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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Q774. What is the use case of S3 Cross Region replication ?

Amazon Web Services (AWS)

Ans. Disaster Recovery and availability

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Q775. 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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Q776. How can EBS Volumes be backed up ?

Amazon Web Services (AWS)

Ans. Through Snapshots

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Q777. Which is the default AWS Region ?

Amazon Web Services (AWS)

Ans. US-EAST-1

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Q778. Difference between List and ArrayList ?

Core Java

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

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Q779. 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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Q780. 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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