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Frequently asked Java Interview Questions and Answers - 296 question(s) found - Order By Rating

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 Q1. What are the benefits of Java over other Programming Languages ?Core Java2020-01-30 09:57:43

Ans. 1. JVM that makes it platform independent and facilitates portability.
2. Garbage Collector that protects from Memory Leaks.
3. Only usage of references and not pointer arithmetic and hence protects the application from memory issues like dangling pointers, memory leaks etc.
4. Support for OOPs that makes application development and maintenance easy.
5. Facilitates library development through use of interface / abstract classes.
6. Facilitates creation of scalable applications.
7. Huge repository of libraries and pool of people with java skill.

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 Q2. difference between ArrayList and array ?Core Java2019-02-06 11:23:55

Ans. ArrayList is a variable length collection class whereas arrays are fixed length primitive structure.

We can use generics with arraylist but not with arrays.

We can store primitive data types within arrays but can't with ArrayList. In ArrayList that needs to be converted to Wrapper objects.


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 Q3. What is your daily work schedule ?General2018-07-24 08:12:47

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  Q4. Difference between Arrays and ArrayList ?Core Java2018-07-22 07:23:59

Ans. Both Arrays and ArrayLists are used to store elements. Elements can be either primitives or objects in case of Arrays, but only objects can be stored in Arraylist. Array is a fixed length data structure while arraylist is variable length collection class. Once created, you cannot change the size of the arrays, but arraylists can dynamically resize itself when needed.Another notable difference between Arrays and Arrayslist is that arary is part of core java programming and array list is part of collection classes

  Sample Code for arrays arraylist

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 Q5. How does multi threading improve performance ?Core Java2018-07-20 17:53:33

Ans. Every process in it's timeline require different resources. Utilization of resources can be optimized when they are shared among different processes or threads. When one thread is sleeping waiting for a peripheral to complete (e.g. a disk write, or a key press from the keyboard), other threads can continue using processor time and hence would lead to better usage of resources.

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 Q6. Between Encrypted Password authentication and IP Authentication , which one would you prefer and why ?Authentication2018-07-16 09:42:17

Ans. IP authentication is very restrictive, if IP changes for some reason then getting the new IP white listed on the server firewall could run your day pretty long. I would prefer encrypted password authentication cause it is not affected by IP changes and not limited to a white listed IP, I could use any different machine and get through authentication without any hassle.

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  Q7. What are the types of authentication used in Web services ?Web Service2018-07-14 11:02:27

Ans. Encrypted User Name / Password
Encrypted Password within Cookie
Encrypted Tokens
IP
Client Certificates
Oauth

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 Q8. How to sort objects based on one of the field ?Core Java2018-07-04 16:23:09

Ans. Using comparable and comparator and sorted collections like TreeSet or TreeMap.

or

use stream api from java 8 onwards which internally refers to comparable and comparator through lambda expressions

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 Q9. Describe structure of a Web application.architecture2018-07-04 16:18:26

Ans. WEB APP |WEB-INF - META-INF | | | META-INF.MF | lib - WEB.xml - Classes

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  Q10. Difference between == and === ?JavaScript2018-07-04 16:16:18

Ans. == compares values === is used in scripting languages for comparing two values as well as there data tpe. like in js,php.

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  Q11. Write code to sort an array.Algorithm2018-07-04 16:15:16

Ans. https://www.geeksforgeeks.org/arrays-sort-in-java-with-examples/

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 Q12. Please explain with example different types of testing ?Testing2018-07-03 15:35:48

Ans. Unit Testing ( Junits )
Integration Testing ( Testing overall flow by calling the entry method or by calling the service end point )
Manual Testing ( End to End Manual User Testing, they way eventually it will be used by end users )
Automation Testing ( Machine replication of end to end testing )

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 Q13. Have you used Java 8 Lambda expressions ?Core Java2018-06-30 13:24:52

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 Q14. Difference between static and dynamic binding ?Design2018-06-30 07:32:21

Ans. Static binding happens at the compile time whereas dynamic binding happens at runtime.

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 Q15. Suppose we make an api call using multithreading, How would you design to make sure that we have received response for all threads before exiting the main thread ?Design2018-06-27 09:55:56

Ans. We can use HashMap for tracking response status for all threads. We can wait every n second by using Thread.sleep and exit the main thread only once we have received response for all threads.

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  Q16. Find Intersection/union between two arrays.Core Java2018-05-13 19:40:34

 This question was recently asked at 'Bristlecone,Amazon Lab126,Amazon,Microsoft,Facebook,NCR,Google'.This question is still unanswered. Can you please provide an answer.


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 Q17. Which spring boot version are you working with ?

Spring Boot2018-05-12 09:01:21

 This question was recently asked at 'Western Governors University (WGU) '.This question is still unanswered. Can you please provide an answer.


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 Q18. What are the different delivery policies in Apache Kafka ?Apache Kafka2018-05-03 06:17:38

Ans. Exactly once , At least once , At max once

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 Q19. Explain Binary SearchAlgorithm2018-02-02 08:37:31

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 Q20. What is abstraction ?Core Java2018-01-30 09:34:29

Ans. The process of hiding the implementation details from the user and providing only functionality.

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 Q21. What is Overriding ?Core Java2018-01-30 09:33:56

Ans. Overriding refers to the Methods with same name and parameters, such that the later over rides the former method.

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 Q22. What is composition ?Core Java2018-01-20 12:20:35

 This question was recently asked at 'MST Solutions'.This question is still unanswered. Can you please provide an answer.


  Sample Code for composition

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 Q23. What is an Interface ?Core Java2018-01-20 12:18:59

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  Sample Code for interface

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  Q24. What is collection framework in Java ?Core Java2017-12-27 19:17:14

Ans. The Java collections framework (JCF) is a set of classes and interfaces that implement commonly reusable collection data structures. Although referred to as a framework, it works in a manner of a library. The JCF provides both interfaces that define various collections and classes that implement them.

  Sample Code for Map

  Sample Code for HashMap

  Sample Code for Treemap

  Sample Code for set

  Sample Code for hashset

  Sample Code for treeset

  Sample Code for list

  Sample Code for arraylist

  Sample Code for linkedlist

  Sample Code for queue

  Sample Code for priorityqueue

  Sample Code for concurrenthashmap

  Sample Code for vector

  Sample Code for stack

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 Q25. What is Method overloading ?Core Java2017-12-26 10:13:48

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 Q26. What is object cloning ?Core Java2017-12-26 09:47:42

Ans. Its is the process of creating exact copy of an object being cloned. In Object class one native method called clone() is there which is meant for Shallow Cloning of Object. Shallow cloning means bitwise copy of an object.In case of primitive data type it will create an exact copy of primitive values as well as variables but if the object contains any reference of an object then it will not copy the referenced object rather it will create the copy of reference variable and assigned it to the old object.

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  Q27. Explain OOps concepts.Core Java2017-12-25 17:29:13

Ans. There are four main OOP concepts in Java. These are:

Abstraction. Abstraction means using simple things to represent complexity. We all know how to turn the TV on, but we don?t need to know how it works in order to enjoy it. In Java, abstraction means simple things like objects, classes, and variables represent more complex underlying code and data. This is important because it lets avoid repeating the same work multiple times.

Encapsulation. This is the practice of keeping fields within a class private, then providing access to them via public methods. It?s a protective barrier that keeps the data and code safe within the class itself. This way, we can re-use objects like code components or variables without allowing open access to the data system-wide.

Inheritance. This is a special feature of Object Oriented Programming in Java. It lets programmers create new classes that share some of the attributes of existing classes. This lets us build on previous work without reinventing the wheel.

Polymorphism. This Java OOP concept lets programmers use the same word to mean different things in different contexts. One form of polymorphism in Java is method overloading. That?s when different meanings are implied by the code itself. The other form is method overriding. That?s when the different meanings are implied by the values of the supplied variables. See more on this below.

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 Q28. Can you explain software design principles cohesion and coupling with an example?Design2017-09-30 07:24:10

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 Q29. What is ORM or Object Relationship Mapping ?Database2017-08-02 08:32:10

Ans. ORM is the mapping technique, which maps object with relational data model. As we know that in java we need objects we can not user data in relational(in table form). So ORM is set of guideline which allows us to map relational data model in object form.

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 Q30. What is the difference between Graph's Breadth first and Depth First algorithm ?Algorithm2017-07-23 10:12:58

Ans. In Breadth first algorithm, all the adjacent nodes of the starting node is visited first and then the same rule is followed while moving inwards whereas

In Depth first algorithm, all the nodes of a single traversal path are visited first till a cycle or an end is found.

For example , given the following entries of adjacent nodes

1,2
1,3
1,6
2,4
2,5
3,6

The Breadth first path would be

1,2,3,6,4,5

and Depth first path would be

1,2,4,5,3,6

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