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

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Q181. Which of the following is not the Dameon process that runs on a hadoop cluster ?

a. JobTracker
b. DataNode
c. TaskTracker
d. TaskNode

Ans. TaskNode

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Q182. What is an instance variable?

a. An instance or object of an class
b. The field of an object
c. Any variable of a class
d. None of the above

Ans. The field of an object

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Q183. Which of the following do you think is the primary reason you would never use a static class even the application doesn't need multiple requests or threads ?

a. Serialization
b. Runtime Polymorphism
c. Lazy Loading
d. Memory

Ans. Runtime Polymorphism

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Q184. Which of the following Java feature promotes access protection or Hiding ?

a. Inheritance
b. Encapsulation
c. Abstraction
d. Composition

Core Java

Ans. Encapsulation

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Q185. What is a Sequence File?

a. A Sequence File contains a binary encoding of an arbitrary number of homogeneous writable objects.
b. A Sequence File contains a binary encoding of an arbitrary number key-value pairs. Each key must be the same type. Each value must be of same type.
c. A Sequence File contains a binary encoding of an arbitrary number of heterogeneous writeable objects.
d. A Sequence File contains a binary encoding of an arbitrary number of Writable Comparable objects, in sorted order.

Ans. A Sequence File contains a binary encoding of an arbitrary number key-value pairs. Each key must be the same type. Each value must be of same type.

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Q186. What is the input to the Reduce function ?

a. One Key and One Value
b. Multiple Keys and Multiple associated Values
c. Multiple Keys and One associated values with each
d. One key and associated values.

Ans. One key and associated values.

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Q187. Which of the following is the implementation language for Map Reduce Framework ?

a. Big Data
b. Hadoop
c. Java
d. C++

Ans. Java

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Q188. Will a for loop like following throw a compilation error ? for(;;);

Ans. No. It will result in infinite loop

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Must know at all levels. Among Top 10 frequently asked questions in Java. Very frequently asked to fresh graduates or less experienced professionals.

Q189. What is Inheritance ?

Core Java

Ans. Its a facility for code reuse and independent extension wherein a derived class inherits the properties of parent class.

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Q190. How is static and dynamic polymorphism achieved in Java ?

Core Java

Ans. Static polymorphism is the polymorphic resolution identified at compile time and is achieved through function overloading whereas dynamic polymorphism is the polymorphic resolution identified at runtime and is achieved through method overriding.

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Q191. How is multiple inheritance implemented in Java ?

Core Java

Ans. There was no multiple inheritance in java before version 8 as implementing multiple interfaces cannot be termed as inheritance.

With Java 8 , came the concept of default methods wherein the class implementing the interface carries the default implementation from the interface and hence facilitating multiple inheritance.

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Q192. Why Java is not considered pure OOP's language ?

Core Java

Ans. There are 2 reasons for it.

1. Usage of Primitive types - Though Java provides classes for the primitive data types but as the usage of primitives is permissible, its considered unpure OOP's language.

2. Usage of Static members - Static members belong to the class and not objects and hence not considered fit for pure OOP's programming.

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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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