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Interview Questions and Answers - Order By Rating

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 Q241. 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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   Like         Discuss         Correct / Improve     databases   sql   cursors   packages     Asked in 5 Companies      basic        frequent


Frequently asked to experienced developers. Recently asked in many US interviews.
  Q242. What is database deadlock ? How can we avoid them?Database
Ans. When multiple external resources are trying to access the DB locks and runs into cyclic wait, it may makes the DB unresponsive.

Deadlock can be avoided using variety of measures, Few listed below -

Can make a queue wherein we can verify and order the request to DB.

Less use of cursors as they lock the tables for long time.

Keeping the transaction smaller.

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   Like         Discuss         Correct / Improve     java   database   architecture     Asked in 7 Companies      expert        frequent


 Q243. Which are the sorted collections ?Core Java
Ans. TreeSet and TreeMap

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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.
  Q244. 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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   Like         Discuss         Correct / Improve     java   collections   hashcode  hash code   equals   collections     Asked in 44 Companies      intermediate        frequent

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  Q245. What do you mean by "Java is a statically typed language" ?Core Java
Ans. It means that the type of variables are checked at compile time in Java.The main advantage here is that all kinds of checking can be done by the compiler and hence will reduce bugs.

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  Q246. Can we have null keys in TreeMap ?Core Java
Ans. No, results in exception.

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


  Q247. Can we overload main method in Java ?Core Java
Ans. Yes, but the overloaded main methods without single String[] argument doesn't get any special status by the JVM. They are just another methods that needs to be called explicitly.

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   Like         Discuss         Correct / Improve     java   main method   overloading   yes-no     Asked in 6 Companies      intermediate        frequent


Frequently asked question in companies using hibernate.
  Q248. Difference between first level and second level cache in hibernate ?Hibernate
Ans. 1. First level cache is enabled by default whereas Second level cache needs to be enabled explicitly.

2. First level Cache came with Hibernate 1.0 whereas Second level cache came with Hibernate 3.0.

3. First level Cache is Session specific whereas Second level cache is shared by sessions that is why First level cache is considered local and second level cache is considered global.

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   Like         Discuss         Correct / Improve     hibernate   orm   hibernate cache   architecture   technical lead   first level cache vs second level cache     Asked in 18 Companies      Intermediate        frequent


 Q249. 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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Very frequently asked Hibernate interview question. Frequently asked in TCS ( based on 2 feedback )
  Q250. What are different types of associations in Hibernate ?Hibernate
Ans. There are 4 types of associations in Hibernate

One to One
One to Many
Many to One
Many to Many

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Very frequently asked if being interviewed for hibernate. Frequently asked in Tata Consultancy (TCS) and Overstock.com
  Q251. Difference between load and get ?Hibernate
Ans. If id doesnt exist in the DB load throws an exception whereas get returns null in that case.get makes the call to DB immediately whereas load makes the call to proxy.

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   Like         Discuss         Correct / Improve     hibernate     Asked in 16 Companies      basic        frequent


  Q252. 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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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies.
  Q253. 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

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Frequently asked question in companies using Hibernate.
  Q254. What is Lazy Initialization in Hibernate ?Hibernate
Ans. It's a feature to lazily initialize dependencies , relationship and associations from the Database. Any related references marked as @OneToMany or @ManyToMany are loaded lazily i.e when they are accessed and not when the parent is loaded.

  Sample Code for Lazy Initialization

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Frequently asked these days as there are major changes in Java 8.
  Q255. 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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   Like         Discuss         Correct / Improve     java   java8   technical lead   technical architect     Asked in 14 Companies      expert        frequent


  Q256. What are Default Methods ?Core Java
Ans. With Java 8, We can provide method definitions in the Interfaces that gets carried down the classes implementing that interface in case they are not overridden by the Class. Keyword "default" is used to mark the default method.

  Sample Code for interface default

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Frequently asked at Manhattan Associates ( Based on 2 feedback )
  Q257. What is a Lambda Expression ? What's its use ?Core Java
Ans. Its an anonymous method without any declaration.

Lambda Expression are useful to write shorthand Code and hence saves the effort of writing lengthy Code.

It promotes Developer productivity, Better Readable and Reliable code.

  Sample Code for lambda

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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)
  Q258. Explain Singleton Design Pattern ?Design
Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html

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 Q259. When does an application throw NullPointerException ?Core Java
Ans. When it tries to access an object element or method using reference which is actually null.

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 Q260. How can we protect an application from throwing a NullPointerException ?
Ans. By having Null Checks.

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Very Frequently asked.
 Q261. Explain throw, throws , try and catch in Java ?Core Java
Ans. throw is used to re throw an exception.throws is used to declare that the method throws the respective exceptions.try block is used to identify if the respective block has thrown any exception.catch is used to catch the exception that has been thrown by the respective try block.

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 Q262. 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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Frequently asked to fresh graduates and less experienced developers. Among the first few questions in many interviews.
  Q263. What are the difference between composition and inheritance in Java?Core Java
Ans. Composition - has-a relationship between objects.
Inheritance - is-a relationship between classes.

Composition - Composing object holds a reference to composed objects and hence relationship is loosely bound.
Inheritance - Derived object carries the base class definition in itself and hence its tightly bound.

Composition - Used in Dependency Injection
Inheritance - Used in Runtime Polymorphism

Composition - Single class objects can be composed within multiple classes.
Inheritance - Single class can only inherit 1 Class.

Composition - Its the relationship between objects.
Inheritance - Its the relationship between classes.

  Sample Code for inheritance

  Sample Code for composition

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Frequently asked to fresh graduates and less experienced.
 Q264. Why do we write public static void main ? Can we use some other syntax too for main ?Core Java
Ans. 1. public is the access modifier that makes the method accessible from anywhere, static is the keyword that makes it accessible even without creating any object, void means it doesn't return anything , String args[] is the array of argument that the method receives.

2. If we use main without the string args , it will compile correctly as Java will treat it as just another method. It wont be the method "main" which Java looks for when it looks to execute the class and hence will throw

Error: Main method not found in class , please define the main method as:
public static void main(String[] args)

3. Main is not a keyword but a special string that Java looks for while initiating the main thread.

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Usually asked to experienced developers.
 Q265. What is a cyclic dependency ?Maven
Ans. A has dependency of B, B has dependency of C and C has dependency of A

With Maven 2 , came transitive dependency wherein in above scenario, C will acts as a dependency of A as if this dependency has been defined directly in A but the negative side is that if it leads to cyclic dependency , it creates problems.

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 Q266. How is Abstraction implemented in Java ?Core Java
Ans. Abstraction is provided in Java by following ways -

Coding to the ( Interfaces / Abstract Classes ) or contracts

By Encapsulating details within classes and exposing the minimal Door ( few public methods )

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 Q267. 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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  Q268. 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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 Q269. 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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 Q270. 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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