Interview Questions and Answers for 'OOP' | Search Interview Question

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Q181. Which of the polymorphism type - static or runtime - is more important ?

Ans. Method overloading / static polymorphism compared to method overriding / runtime polymorphism has very limited usage as it just opens up an alternate way of defining a different method with the same name.

Method Overriding on other hand opens up many other features like contracting , interfacing , pluging development and hence development of libraries and frameworks.

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Q182. How to instantiate jsp variable from another jsp?

JSP

Ans. using session attribute.

session.setAttribute("userId",userId);

in first jsp

int userId=session.getAttribute("userId");

in second jsp;

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Q183. Find unique values between two arrays using single for loop ?

Core Java

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Q184. What is virtual table with respect to method overriding in Java ?

Core Java

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Q185. How is the virtual method table implemented in Java?

Core Java

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Q186. How many VTables are there for each class ?

Core Java

Ans. There is one VTable for each class.

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Q187. Can a class extend itself in Java ?

Core Java

Ans. No

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Q188. Difference between hadoop 1.x and 2.x?

Apache Hadoop

Ans. Hadoop 1.x

It supports only MapReduce (MR) processing model.
It has limited scaling of nodes. Limited to 4000 nodes per cluster.
It has single Namenode to manage the entire namespace.
It has Single-Point-of-Failure (SPOF)
Works on concepts of slots – slots can run either a Map task or a Reduce task
MR has to do both processing and cluster resource management.

Hadoop 2.x

It supports MR as well as other distributed computing models like Spark, Hama, etc
It has better scalability. Scalable up to 10000 nodes per cluster.
Works on concepts of containers. Using containers can run generic tasks.
It has Multiple Namenode servers manage multiple namespace.
YARN does cluster resource management and processing is done using different processing models.

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Q189. Difference between group and cogroup?

Apache Hadoop

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Q190. How Object-Oriented Programming is implemented in JavaScript? How they differ from other languages?

Javascript

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Q191. What are the static class members loaded into the memory ?

OOP

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Q192. Can we initialize final fields within the constructor ? Why ?

Core Java

Ans. Yes, Because final fields needs to be initialized before the construction of the object completes. Not necessarily at the time of class loading.

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Q193. What is the relationship between Vehicle and Engine in this example ?

public class Vehicle {
   Enginer engine;
   public void move(){
      engine = new Engine();
      engine.start();
   }
}

Core Java

a. Composition ( Vehicle has a Engine )

b. Composition ( Engine has a Vehicle )

c. Inheritance ( Vehicle is a Engine )

d. Inheritance ( Engine is a Vehicle )

Ans.a. Composition ( Vehicle has a Engine )

Q194. What is the relationship between Car and Vehicle in the following code ?

public class Car extends Vehicle{
   Engine engine;

   public static void main(String[] args){
      Vehicle vehicle = new Car();
      car.move();
   }

   public void move(){
      engine = new Engine();
      engine.start();
   }
}

Core Java

a. Composition ( Vehicle has a Car )

b. Composition ( Car has a Vehicle )

c. Inheritance ( Vehicle is a Car )

d. Inheritance ( Car is a Vehicle )

Ans.d. Inheritance ( Car is a Vehicle )

Q195. What is the problem with the following code ?

public class Car extends Vehicle{
   Vehicle vehicle;

   Car(){
      super();
      this.vehicle = new Vehicle();
   }
}

Core Java

a. There is an Inheritance as well as Composition relationship between Vehicle and Car which is not permitted

b. We cannot initialize the parent class instance within the constructor

c. Call to super is illegal

d. There is no problem

Ans.d. There is no problem

Q196. Which of the following Java feature specify hash-a relationship between objects ?

Core Java

a. Inheritance

b. Composition

c. Polyorphism

d. Encapsulation

Ans.b. Composition

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