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Java Concurrency in Practice


   




Core java - Interview Questions and Answers for 'Concur' - 19 question(s) found - Order By Newest

Frequently asked to fresh graduates and less experienced developers.
 Q1. Explain multithreading in Java ?Core Java
Anonymous
Ans. 1. Multithreading provides better interaction with the user by distribution of task

2. Threads in Java appear to run concurrently, so it provides simulation for simultaneous activities.The processor runs each thread for a short time and switches among the threads to simulate sim-ultaneous execution (context-switching) and it make appears that each thread has its own processor.By using this feature, users can make it appear as if multiple tasks are occurring simultaneously when, in fact, each is running for only a brief time before the context is switched to the next thread.

3. We can do other things while waiting for slow I/O operations.In the java.iopackage, the class InputStreamhas a method, read(), that blocks until a byte is read from the stream or until an IOExceptionis thrown. The thread that executes this method cannot do anything elsewhile awaiting the arrival of another byte on the stream.

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   Like      Discuss      Correct / Improve     java   threads   multi threading  concurrency   multithreading     Hamsini ECommerce   Cognizant (CTS)  Cumulus Systems  Cognizant (CTS)      intermediate        frequent

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 Q2. What is the use of runnable interface if we can always create a new thread using Thread class ?Core Java
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Ans. It's a choice to be made whether to use first approach ( Thread class ) or second approach ( runnable interface ) by the programmer. The second facility has been given for cases where your class is already extending some parent class and hence cannot extend another class ( for Thread ) as Java doesn't allow multiple inheritance.

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 Q3. What is a ConcurrentHashMap ?Core Java
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Ans. ConcurrentHashMap is a hashMap that allows concurrent modifications from multiple threads as there can be multiple locks on the same hashmap.

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   Like      Discuss      Correct / Improve     java   collections   hashmap   map   concurrenthashmap   concurrenthashmap  concurrency   general electric   ge     Cognizant (CTS)  Synechron  General Electric  MakeMyTrip.com  Nomura Securities  Xpanxion  Royal Bank of Scotland (RBS)  ProKarma  Talentica  Citi  EdgeVerve Systems  Six Dee Telecom  ReqRoute  Qumulo  Goldman Sachs  HSBC Holdings  AlertMe.com  BlackRock  Helpchat  Bally Technologies  Hubzu  Xpanxion  Coromandel Infotech  Paytm  YuMe  InfoGain  Markit  Wells Fargo  Geometric  Acloudzyn Technologies  Roposo  Nagarvision        rare


 Q4. What is ConcurrentLinkedDeque ?Core Java
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Ans. It's a Collections concrete class that provides implementation of a Double Ended queue that allows concurrent insertion, removal, and access operations that can be executed safely across multiple threads.

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 Q5. What are the advantages and disadvantages of CopyOnWriteArrayList ?Core Java
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Ans. This collections class has been implemented in such a manner that it can never throw ConcurrentModificationException. As it performs update and write operations by creating a new copy of ArrayList, It's slower compared to ArrayList.

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 Q6. What is ConcurrentModificationException ?Core Java
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Ans. This is the exception that is thrown when we try to modify the non concurrent collection class while iterating through it.

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 Q7. What is the use of Synchronized block ?Core Java

Ans. The goal of a synchronised block is to achieve mutual exclusion i.e at one time, the segment of the code should be executed by single thread only and hence the lock needs to be retrieved before executing the segment and then released.

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 Q8. Difference between concurrentHashMap and HashTable ?Core Java2017-01-29 18:37:04

Ans. HashTable locks the complete collection to provide synchronization whereas ConcurrentHashMap only locks segments to achieve synchronization and hence better efficient and faster.

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 Q9. isnt the use of HashTable and ConcurrentHashMap the same, i.e providing synchronized map collection ?Core Java2017-01-29 18:38:52

Ans. Yes, they both aim at providing synchronized access to the Map collection. The only difference is in their implementation. ConcurrentHashMap came after HashTable and hence technically more efficient as it doesn't lock the complete map while accessing it.

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 Q10. How do threads share information ?Core Java2017-02-27 07:33:36

 This question was recently asked at 'Concurrent Technologies Corporation (CTC)'.This question is still unanswered. Can you please provide an answer.


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   Like      Discuss      Correct / Improve     threads     Concurrent Technologies Corporation (CTC)


 Q11. What is the use of java.util.concurrent package in Java ?Core Java2017-04-30 09:50:16

 This question is still unanswered. Can you please provide an answer.


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 Q12. What are the advantages and disadvantages of using lock classes from java.util.concurrent.locks vs. synchronized methods ?Core Java2017-05-07 19:30:42

Ans. http://www.devinline.com/2015/10/Lock-Vs-synchronized-in-java.html

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   Like      Discuss      Correct / Improve     java.util.concurrent.locks  synchronization  synchronized methods


 Q13. Explain Java 8 concurrency mechanism.Core Java2017-07-22 07:52:01

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


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 Q14. If a Map needs to be accessed simultaneously by multiple threads, which collection class should be used ? Core Java2017-08-17 11:01:07

Ans. ConcurrentHashMap

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   Like      Discuss      Correct / Improve     map  concurrenthashmap  multithreading


 Q15. Which are the thread safe / synchronized / concurrent classes in java collections ?Core Java2018-03-10 19:41:26

Ans. Stack
Properties
Vector
BlockingQueue
ConcurrentMap
ConcurrentNavigableMap

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   Like      Discuss      Correct / Improve     collections  concurrent classes


 Q16. What are the different ways to avoid multi Threading related problems in Java ?Core Java2018-07-20 17:58:09

Ans. Synchronization,
Concurrent classes,
Volatile keyword,
Implementing concurrent Lock interface,
Immutable classes

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 Q17. Why Concurrent Collection Classes are fail-fast in Java ?Core Java2018-07-20 18:02:59

 This question is still unanswered. Can you please provide an answer.


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 Q18. Isnt the use of HashTable and ConcurrentHashMap the same, i.e providing synchronized map collection ?Core Java2018-08-30 08:37:45

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


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   Like      Discuss      Correct / Improve     synchronized collections  hashtable  ConcurrentHashMap     Tata Consultancy


 Q19. How many read and write operations are provided at the same time by ConcurrentHashMaps ?Core Java2018-11-14 12:49:48

Ans. ConcurrentHashMaps provide unlimited read operation fro multi threaded environment. For write operation only one thread can change value for particular segment of map.

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   Like      Discuss      Correct / Improve     ConcurrentHashMap     Synechron




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