Frequently asked Interview Questions and Answers

Interview Questions and Answers - Order By Newest

Q161. Explain Inner Classes ?

Ans. The accessibility (public, protected, etc.) of the inner class is defined by the outer class.

Just like top-level classes, an inner class can extend a class or can implement interfaces.

Similarly, an inner class can be extended by other classes, and an inner interface can be implemented or extended by other classes or interfaces.

An inner class can be declared final or abstract.Inner classes can have inner classes, but you will have a hard time reading or understanding such complex nesting of classes.

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Q162. When you will synchronize a piece of your code?

Ans. When you expect your code will be accessed by different threads and these threads may change a particular data causing data corruption.

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Q163. What is connection pooling?

Database

Ans. It's a technique to allow multiple clients to make use of a cached set of shared and reusable connection objects providing access to a database or other resource.

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Q164. Difference between throw and throws ?

Core Java

Ans. throw is used to explicitly throw an exception especially custom exceptions, whereas throws is used to declare that the method can throw an exception.

We cannot throw multiple exceptions using throw statement but we can declare that a method can throw multiple exceptions using throws and comma separator.

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Q165. What is an Object ?

Core Java

Ans. Object is a run time entity whose state is stored in fields and behavior is shown via methods. Methods operate on an object's internal state and serve as the primary mechanism for object-to-object communication.

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Q166. 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.

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Q167. What is Comparable Interface?

Core Java

Ans. It is used to sort collections and arrays of objects using the collections.sort() and java.utils. The objects of the class implementing the Comparable interface can be ordered.

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Q168. What are use cases?

Process

Ans. It is part of the analysis of a program and describes a situation that a program might encounter and what behavior the program should exhibit in that circumstance.

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Q169. What is the difference between a break statement and a continue statement?

Core Java

Ans. Break statement results in the termination of the statement to which it applies (switch, for, do, or while). A continue statement is used to end the current loop iteration and return control to the loop statement.

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Q170. What is the use of HashCode in objects ?

Core Java

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

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Q171. What will be the output of the following code ?

String s1 = "Buggy Bread";
String s2 = "Buggy Bread";
if(s1 == s2)
System.out.println("equal 1");
String n1 = new String("Buggy Bread");
String n2 = new String("Buggy Bread");
if(n1 == n2)
System.out.println("equal 2");

Core Java

Ans. equal 1

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Q172. Which markup languages can be used in restful web services ?

Rest

Ans. XML and JSON ( Javascript Object Notation ).

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Q173. Difference between Inner and Outer Join ?

Database

Ans. Inner join is the intersection of two tables on a particular columns whereas Outer Join is the Union of two tables.

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Q174. What is a Cursor ?

Database

Ans. It's a facility that allows traversal over the records pulled from a table or combination of tables. Its like iterator in Java.

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Very Frequently asked. Favorite question in walkins and telephonic interviews. Usually among first few questions. Asked in different variants. Must know for intermediate and expert professionals.Among Top 10 frequently asked questions.

Q175. What is rule regarding overriding equals and hashCode method ?

Core Java

Ans. A Class must override the hashCode method if its overriding the equals method.

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Q176. Can we have null keys in TreeMap ?

Core Java

Ans. No, results in exception.

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Q177. What are the different types of inheritance in Hibernate ?

Hibernate

Ans. Table Per Class , Table per Sub Class , Table per Concrete Class

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Q178. What is lazy fetching in Hibernate ?

Hibernate

Ans. Lazy fetching is the technique of not loading the child objects when parent objects are loaded. By default Hibernate does not load child objects. One can specify whether to load them or not while doing the association.

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Frequently asked these days as there are major changes in Java 8.

Q179. What are new features introduced with Java 8 ?

Core Java

Ans. Lambda Expressions , Interface Default and Static Methods , Method Reference , Parameters Name , Optional , Streams, Concurrency.

Sample Code for Lambda

Sample Code for interface default

Sample Code for Optional

Sample Code for Streams

Sample Code for java.time

Sample Code for Predicate

Sample Code for Consumer

Sample Code for MapMerge

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Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback)

Q180. Explain Singleton Design Pattern ?

Design

Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html

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Q181. How can we protect an application from throwing a NullPointerException ?

Ans. By having Null Checks.

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Q182. Why is a constant defined as a static final in Java?

Core Java

Ans. Final makes sure that the value doesn't change after initialization and static makes sure that there is only one copy that can be shared across objects.

Making it non static will unnecessarily create a different copy per object wherein the same value will kept for all copies ( as its final and cannot be changed ).

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Q183. What is Criteria in Hibernate ?

Hibernate

Ans. Criteria is a simplified API for retrieving entities by composing Criterion objects.

For example - session.createCriteria(Employee.class).add( Restrictions.like("name", "A%") ).list();

will return all employee objects having name starting with A.

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Q184. 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.

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Q185. Which UML diagrams you usually use for design ?

Design

Ans. Use Case Diagram, Component Diagram for High level Design and Class Diagram , Sequence Diagram for low level design.

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Q186. What is your role in current position ?

General

Ans. I am working as a Software System Analyst that specializes in understanding Business Requirements, Analyzing them , Performs Cost / Benefit analysis, Make suggestions to business , translate the business requirements into technical requirements, Discuss their feasibility with the technical team, performs sizing in coordination with developers and prepare high level design document.

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Q187. What is Jenkins ?

Jenkins

Ans. It is a continuous integration tool written in Java.

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Q188. Which takes more memory - float or Float ?

Core Java

Ans. float is a native data type whereas Float is a class. A Float object will always take more memory than float variable as there are metadata overheads with the objects.

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Q189. What is collision in hash collections ?

Core Java

Ans. Collision is the situation when two different elements have the same Hash Code.

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Q190. Which of the collections allows null as the key ?

a. HashTable
b. HashMap
c. TreeMap
d. LinkedHashMap

Core Java

Ans. HashMap

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