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

Interview Questions and Answers for 'OLA' - 53 question(s) found - Order By Newest

Q1. Explain OOPs

or

Explain OOPs Principles

or

Explain OOPs Concepts

or

Explain OOPs features

or

Tell me something about OOPs

Core Java

Ans. OOPs or Object Oriented Programming is a Programming model which is organized around Objects instead of processes. Instead of a process calling series of processes, this model stresses on communication between objects. Objects that all self sustained, provide security by encapsulating it's members and providing abstracted interfaces over the functions it performs. OOP's facilitate the following features

1. Inheritance for Code Reuse
2. Abstraction for modularity, maintenance and agility
3. Encapsulation for security and protection
4. Polymorphism for flexibility and interfacing

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve oops oops features Asked in 260 Companies basic frequent}

Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.

Q2. What is the difference between ArrayList and LinkedList ?

Core Java

Ans. Underlying data structure for ArrayList is Array whereas LinkedList is the linked list and hence have following differences -

1. ArrayList needs continuous memory locations and hence need to be moved to a bigger space if new elements are to be added to a filled array which is not required for LinkedList.

2. Removal and Insertion at specific place in ArrayList requires moving all elements and hence leads to O(n) insertions and removal whereas its constant O(1) for LinkedList.

3. Random access using index in ArrayList is faster than LinkedList which requires traversing the complete list through references.

4. Though Linear Search takes Similar Time for both, Binary Search using LinkedList requires creating new Model called Binary Search Tree which is slower but offers constant time insertion and deletion.

5. For a set of integers you want to sort using quicksort, it's probably faster to use an array; for a set of large structures you want to sort using selection sort, a linked list will be faster.

Sample Code for ArrayList

Sample Code for LinkedList

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve collections java data structures arraylist linkedlist arraylist vs linkedlist Asked in 61 Companies Basic frequent}

Try 1 Question(s) Test

Frequently asked in Infosys and HCL Technologies ( Based on 2 feedback )

Q3. What are different ways of object creation in Java ?

Core Java

Ans. Using new operator - new xyzClass()

Using factory methods - xyzFactory.getInstance( )

Using newInstance( ) method - (Class.forName(xyzClass))emp.newInstance( )

By cloning an already available object - (xyzClass)obj1.clone( )

Sample Code for object initialization using clone

Sample Code for object initialization using getInstance

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops object creation new operator class.forname cloning ebay Asked in 9 Companies expert}

Basic and Very Frequently asked.

Q4. What is Polymorphism in Java ?

Core Java

Ans. Polymorphism means the condition of occurring in several different forms.

Polymorphism in Java is achieved in two manners

1. Static polymorphism is the polymorphic resolution identified at compile time and is achieved through function overloading whereas

2. Dynamic polymorphism is the polymorphic resolution identified at runtime and is achieved through method overriding.

Sample Code for overloading

Sample Code for overriding

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve polymorphism object oriented programming (oops) oops concepts oops concepts Asked in 108 Companies Basic frequent}

Try 2 Question(s) Test

Very Frequently asked. Have been asked in HCL Technologies very frequently ( based on 3 feedback ). Among first few questions in many interviews.

Q5. Differences between abstract class and interface ?

Core Java

Ans. Abstract classes can have both abstract methods ( method declarations ) as well as concrete methods ( inherited to the derived classes ) whereas Interfaces can only have abstract methods ( method declarations ).

A class can extend single abstract class whereas it can implement multiple interfaces.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java classes abstract class interfaces abstract class vs interface abstract classes vs interfaces Asked in 82 Companies basic frequent}

Q6. Which of the following combination of keywords is illegal in Java ?

a. static and transient
b. transient and final
c. static and synchronized
d. abstract and final

Core Java

Ans. abstract and final

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java keywords Asked in 2 Companies basic}

Frequently asked in Infosys India

Q7. What is a String Pool ?

Core Java

Ans. String pool (String intern pool) is a special storage area in Java heap. When a string is created and if the string already exists in the pool, the reference of the existing string will be returned, instead of creating a new object and returning its reference.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops string string class string pool heap memory Asked in 31 Companies intermediate frequent}

Try 2 Question(s) Test

Very Frequently asked to fresh graduates and less experienced. Favorite question in Walk in drives. Frequently asked in Indian Services companies.

Q8. Difference between Overloading and Overriding ?

Core Java

Ans. Overloading - Similar Signature but different definition , like function overloading.

Overriding - Overriding the Definition of base class in the derived class.

Sample Code for overloading

Sample Code for overriding

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops overloading overriding oops concepts basic interview question overloading vs overriding Asked in 86 Companies basic frequent}

Try 1 Question(s) Test

Advanced level question usually asked to senior developers , leads and architects.

Q9. How does volatile affect code optimization by compiler?

Core Java

Ans. Volatile is an instruction that the variables can be accessed by multiple threads and hence shouldn't be cached. As volatile variables are never cached and hence their retrieval cannot be optimized.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java keywords volatile synchronization compiler optimization variable caching architecture Asked in 3 Companies expert}

Q10. Difference between JVM, JRE and JDK ?

Core Java

Ans. JDK(Java Development kit) = Development Kit comprising of JVM , library and development tools for developers

JRE (Java Run time Environment) - Comprise of JVM and set of libraries

JVM(Java Virtual Machine) = Interpreter which reads the .class file line by line.

When we install JDK, JRE also get installed so we can write,compile and excute our code. Used by developer. Without JDK we can only execute the program using JRE.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve jvm jre jdk jvm vs jre vs jdk Asked in 4 Companies}

Very Frequently asked across all type of companies and across all levels.

Q11. Difference between Public, Private, Default and Protected ?

Core Java

Ans. Private - Not accessible outside object scope.

Public - Accessible from anywhere.

Default - Accessible from anywhere within same package.

Protected - Accessible from object and the sub class objects.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oop access specifier public private default protected public vs private vs default vs protected Asked in 12 Companies basic frequent}

Try 1 Question(s) Test

Frequently asked question for intermediate developers. Frequently asked in HCL Technologies and EPAM.

Q12. What is Volatile keyword used for ?

Core Java

Ans. Volatile is a declaration that a variable can be accessed by multiple threads and hence shouldnt be cached.

Sample Code for volatile

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops synchronization volatile java keywords Asked in 42 Companies intermediate frequent}

Try 1 Question(s) Test

Very frequently asked.Usually among first few questions.

Q13. What is MVC ?

Design

Ans. MVC is a Design Pattern that facilititates loose coupling by segregating responsibilities in a Web application

1. Controller receives the requests and handles overall control of the request
2. Model holds majority of the Business logic, and
3. View comprise of the view objects and GUI component

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve j2ee mvc mvc design pattern design pattern struts spring web application web frameworks ebay Asked in 60 Companies basic frequent}

Try 1 Question(s) Test

Frequently asked to fresh graduates and less experienced.

Q14. Difference between Composition and Inheritance ?

Core Java

Ans. Inheritance means a object inheriting reusable properties of the base class. Compositions means that an abject holds other objects.

In Inheritance there is only one object in memory ( derived object ) whereas in Composition , parent object holds references of all composed objects.

From Design perspective - Inheritance is "is a" relationship among objects whereas Composition is "has a" relationship among objects.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops oops concepts inheritance object oriented programming (oops) oops concepts composition object oriented programming (oops) oops concepts difference between basic interview question Asked in 12 Companies basic frequent}

Try 2 Question(s) Test

Frequently asked in high end product companies. Frequently asked in Deloitte.

Q15. How is Hashmap internally implemented in Java ?

Core Java

Ans. https://medium.com/javarevisited/internal-working-of-hashmap-in-java-97aeac3c7beb#:~:text=HashMap%20internally%20uses%20HashTable%20implementation,the%20entries%20into%20the%20map.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve hashmap collections hashmap internal implementation Asked in 20 Companies expert frequent}

Q16. What is Generalization and Specialization in terms of casting ?

Core Java

Ans. Generalization or UpCasting is a phenomenon where a sub class is prompted to a super class, and hence becomes more general. Generalization needs widening or up-casting. Specialization or DownCasting is a phenomenon where a super class is narrowed down to a sub class. Specialization needs narrowing or down-casting.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java data types casting type casting up casting type casting downcasting type casting generalization specialization Asked in 2 Companies}

Q17. What is constructor chaining and how is it achieved in Java?

Core Java

Ans. A child object constructor always first needs to construct its parent. In Java it is done via an implicit call to the no-args constructor as the first statement

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java constructor constructor chaining oops call constructor explicitly Asked in 3 Companies}

Try 2 Question(s) Test

Usually asked to entry level software developers.

Q18. Write a program to swap two variables without using third

Core Java

Ans. public static void main(String[] args) {
   int num1 = 1;
   int num2 = 2;
   num1 = num1^num2;
   num2 = num1^num2;
   num1 = num1^num2;
   System.out.print("num1 = " + num1 +", num2 = "+num2);
}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve code coding Asked in 37 Companies basic frequent}

Q19. What is JSON ?

Json

Ans. JSON is "JavaScript Object Notation", primarily used for client-server or server-server communication. Its a much lighter and readable alternative to XML. JSON is language independent and is easily parse-able in all programming languages.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve json markup language client server communication Asked in 26 Companies basic frequent}

Try 2 Question(s) Test

Frequently asked in CTS ( Based on 2 feedback )

Q20. What is the difference between comparable and comparator in java.util pkg?

Core Java

Ans. Comparable interface is used for single sequence sorting i.e.sorting the objects based on single data member where as comparator interface is used to sort the object based on multiple data members.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java java.util comparable comparator collections Asked in 23 Companies basic frequent}

Q21. What does String intern() method do?

Core Java

Ans. intern() method keeps the string in an internal cache that is usually not garbage collected.

Moreover provide reference for scp object for corresponding string object present in heap memory.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java string class string intern method garbage collection advanced Asked in 2 Companies expert}

Q22. What is a Webdriver ?

Testing

Ans. Selenium WebDriver is a tool for automating web application testing.It helps in replicating the manual tester behavior like keyboard entry, mouse events etc and then matching the output against the expected.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve selenium webdriver Asked in 37 Companies}

Q23. What is abstraction ?

Design

Ans. Abstraction is a process of hiding the implementation details and describing only the functionality to the user.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve bstraction oops concepts oops principle Asked in 22 Companies}

Q24. What is a Class ?

Core Java

Ans. A class is a blue print or Mold using which individual objects are created. A class can contain fields and methods to describe the behavior of an object.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java oops class basic interview question Asked in 1 Companies basic frequent}

Q25. What is the use of HashCode in objects ?

Core Java

Ans. Hashcode is used for bucketing in Hash implementations like HashMap, HashTable, HashSet etc.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java string hashcode hash code string comparison hashtable Asked in 17 Companies basic frequent}

Q26. Can we have null keys in TreeMap ?

Core Java

Ans. No, results in exception.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve java collections treemap Asked in 6 Companies Basic frequent}

Q27. Which Software Development methodology is being used in your current Job ?

General

Ans. We are using Agile methodology. I attend daily stand up where the development leads takes the status of assigned stories, achievements, any bottlenecks or challenges. We follow iteration of 2 weeks.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve sdlc agile methodology software system analyst software developer interview development lead project lead interview Asked in 14 Companies frequent}

Frequently asked in face to face interviews.

Q28. Write a program to print fibonacci series.

Core Java

Ans. int count = 15;
int[] fibonacci = new int[count];
fibonacci[0] = 0;
fibonacci[1] = 1;
for(int x=2; x < count; x++){
fibonacci[x] = fibonacci[x-1] + fibonacci[x-2];
}

for(int x=0; x< count; x++){
System.out.print(fibonacci[x] + " ");
}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve ebay fibonacci series Asked in 66 Companies basic frequent}

Q29. When do we generally get this database error - integrity constraint violated - parent key not found ?

Ans. This error most likely will be thrown during an insert statement, while inserting a value within a foreign key column which doesnt exist within the Parent column. For example - Trying to add a dept number reference within a Employee Table when the Dept doesnt exist in the Dept Table.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve database integrity constraint error integrity constraint violated}

Q30. Why can't we declare a class abstract as well as final ?

Core Java

Ans. Abstract means that the class is only meant to be subclassed whereas final means that it cannot be subclassed so both concepts - abstract and final are actually mutually exclusive and hence not permitted together.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve abstract final java keywords Asked in 1 Companies}

Search Interview Questions

Help us and Others Improve. Please let us know the questions asked in any of your previous interview.