Threads In Java Interview Questions And Answers Pdf

threads in java interview questions and answers pdf

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Top 100+ Java Multithreading Interview Questions and Answers - 1

Threads consumes CPU in best possible manner, hence enables multi processing. Multi threading reduces idle time of CPU which improves performance of application. Advantage of Thread : Suppose one thread needs 10 minutes to get certain task, 10 threads used at a time could complete that task in 1 minute, because threads can run parallely. Thread are subdivision of Process. One or more Threads runs in the context of process. Threads can execute any part of process.

And same part of process can be executed by multiple Threads. Processes have their own copy of the data segment of the parent process while Threads have direct access to the data segment of its process. Processes have their own address while Threads share the address space of the process that created it. Process creation needs whole lot of stuff to be done, we might need to copy whole parent process, but Thread can be easily created.

Processes can easily communicate with child processes but interprocess communication is difficult. While, Threads can easily communicate with other threads of the same process using wait and notify methods. In process all threads share system resource like heap Memory etc.

Any change made to process does not affect child processes, but any change made to thread can affect the behavior of the other threads of the process. Example to see where threads on are created on different processes and same process.

This is very basic threading question. Threads can be created in two ways i. Runnable interface or extending java. Thread class and then extending run method. Thread has its own variables and methods, it lives and dies on the heap.

But a thread of execution is an individual process that has its own call stack. Thread are lightweight process in java. Yes, Threads have their own stack.

This is very interesting question, where interviewer tends to check your basic knowledge about how threads internally maintains their own stacks. Question 5. We should implement Runnable interface or extend Thread class. What are differences between implementing Runnable and extending Thread? Well the answer is you must extend Thread only when you are looking to modify run and other methods as well. If you are simply looking to modify only the run method implementing Runnable is the best option Runnable interface has only one abstract method i.

Differences between implementing Runnable interface and extending Thread class -. The solution to question is quite simple, Thread behaviour is unpredictable because execution of Threads depends on Thread scheduler, thread scheduler may have different implementation on different platforms like windows, unix etc. Same threading program may produce different output in subsequent executions even on same platform.

Threads are lightweight process only if threads of same process are executing concurrently. But if threads of different processes are executing concurrently then threads are heavy weight process. Question 8. How can you ensure all threads that started from main must end in order in which they started and also main should end in last? Interviewers tend to know interviewees knowledge about Thread methods.

So this is time to prove your point by answering correctly. We can use join method to ensure all threads that started from main must end in order in which they started and also main should end in last. In other words waits for this thread to die. Calling join method internally calls join 0 ;. Types of join method with programs- 10 salient features of join. Question 9. What is difference between starting thread with run and start method? This is quite interesting question, it might confuse you a bit and at time may make you think is there really any difference between starting thread with run and start method.

When you call start method, main thread internally calls run method to start newly created Thread, so run method is ultimately called by newly created thread. When you call run method main thread rather than starting run method with newly thread it start run method by itself.

Question What is significance of using Volatile keyword? Java allows threads to access shared variables. As a rule, to ensure that shared variables are consistently updated, a thread should ensure that it has exclusive use of such variables by obtaining a lock that enforces mutual exclusion for those shared variables.

If a field is declared volatile , in that case the Java memory model ensures that all threads see a consistent value for the variable. Can we have volatile methods in java? Volatile can be used as a keyword against the variable, we cannot use volatile against method declaration. Variables cannot be synchronized. Volatile does not acquire any lock on variable or object, but Synchronization acquires lock on method or block in which it is used.

Volatile variables are not cached, but variables used inside synchronized method or block are cached. When volatile is used will never create deadlock in program, as volatile never obtains any kind of lock. But in case if synchronization is not done properly, we might end up creating dedlock in program. Synchronization may cost us performance issues, as one thread might be waiting for another thread to release lock on object.

But volatile is never expensive in terms of performance. No, we cannot start Thread again , doing so will throw runtimeException java. The reason is once run method is executed by Thread, it goes into dead state.

Thinking of starting thread again and calling start method on it which internally is going to call run method for us is some what like asking dead man to wake up and run. As, after completing his life person goes to dead state. What is race condition in multithreading and how can we solve it? This is very important question, this forms the core of multi threading, you should be able to explain about race condition in detail. When more than one thread try to access same resource without synchronization causes race condition.

So we can solve race condition by using either synchronized block or synchronized method. When no two threads can access same resource at a time phenomenon is also called as mutual exclusion. What if two threads try to read same resource without synchronization? What if two threads try to write to same resource without synchronization? This is very must know question for all the interviewees, you will most probably face this question in almost every time you go for interview.

Threads can communicate with each other by using wait , notify and notifyAll methods. Every Object has a monitor, acquiring that monitors allow thread to hold lock on object. But Thread class does not have any monitors. Now, Straight forward question that comes to mind is how thread acquires object lock by. Is it important to acquire object lock before calling wait , notify and notifyAll? If we call these methods without acquiring object lock i.

IllegalMonitorStateException is thrown at runtime. Wait method needs to enclosed in try-catch block, because it throws compile time exception i.

How can you solve consumer producer problem by using wait and notify method? Here come the time to answer very very important question from interview perspective.

Interviewers tends to check how sound you are in threads inter communication. Because for solving this problem we got to use synchronization blocks, wait and notify method very cautiously. If you misplace synchronization block or any of the method, that may cause your program to go horribly wrong. As soon as size is less than 2, producer will start producing. As soon as size is greater than 0, consumer will start consuming. We will create sharedQueue that will be shared amongst Producer and Consumer.

We will now start consumer and producer thread. Note: it does not matter order in which threads are started because rest of code has taken care of synchronization and key points mentioned above. How to solve Consumer Producer problem without using wait and notify methods, where consumer can consume only when production is over.

In this problem, producer will allow consumer to consume only when 10 products have been produced i. We will approach by keeping one boolean variable productionInProcess and initially setting it to true, and later when production will be over we will set it to false. How can you solve consumer producer pattern by using BlockingQueue? BlockingQueue is a interface and we will use its implementation class LinkedBlockingQueue. What is deadlock in multithreading?

Write a program to form DeadLock in multi threading and also how to solve DeadLock situation. What measures you should take to avoid deadlock?

Top 100 Java Interview Questions and Answers (Download PDF)

Java Collection Classes are fail fast which means that if the Collection will be changed while some thread is traversing over it using iterator, the iterator. Concurrent collection classes supports full concurrency of retrievals and adjustable expected concurrency for updates. A thread can enter the waiting state by the following ways. It can also enter the waiting state by invoking its deprecated suspend method. In Multi Threaded programming, multiple threads are executing concurrently that improves the performance because CPU is not idle incase some thread is waiting to get some resources. The life cycle of threads in Java is very similar to the life cycle of processes running in an operating system.

We will also look into Concurrency interview questions and answers because both multithreading and concurrency go hand in hand. Thread is one of the popular topics in java interview questions. Here I am listing down most of the important java multithreading interview questions from interview perspective, but you should have good knowledge on java threads to deal with follow up questions. A process is a self contained execution environment and it can be seen as a program or application whereas Thread is a single task of execution within the process. Java runtime environment runs as a single process which contains different classes and programs as processes. Thread can be called lightweight process.


Top Three Threading Questions Asked In Interviews? *Read below to find answers for these and other important questions. 1/


Java Multithreading and Concurrency Interview Questions

Hi Javin, Excellent piece! I have a question tho, is there a decent step by step guide out there for working through threading in Java? Reason I ask is, I find it is helpful to do assignments with the concept and while I do have knowledge about threading in java I am just not sure I have a complete picture. Again excellent work, I hope to see more articles!

Threads consumes CPU in best possible manner, hence enables multi processing. Multi threading reduces idle time of CPU which improves performance of application. Advantage of Thread : Suppose one thread needs 10 minutes to get certain task, 10 threads used at a time could complete that task in 1 minute, because threads can run parallely.

Multithreading and Synchronization are considered as the typical chapter in java programming. In game development companies, multithreading related interview questions are asked mostly. A list of frequently asked java multithreading and concurrency interview questions is given below. Multithreading is a process of executing multiple threads simultaneously.

Download PDF We have compiled the most frequently asked Java Interview Questions and Answers that will help you prepare for the Basic Java interview questions that an interviewer might ask you during your interview. In this list of Basic Java interview questions, we have covered all commonly asked basic and advanced Core Java interview questions with detailed answers to help you clear the job interview. The following list contains important Core Java interview questions for freshers as well as Java interview questions and answers for experienced programmers to help them prepare for the interview.

Java Questions

Interview Questions on MultiThreading are among my favourites. With a number of complex scenarios possible, this topic can seriously test an interview candidate. This interview guide attempt to explain the important concepts with a number of examples. Threads allow Java code to run in parallel. We are creating a Cricket Statistics Application. Let's say the steps involved in the application are. Run individually this program takes minutes.

Хотя три дня назад, когда раздался звонок, Токуген Нуматака был полон сомнений и подозрений, теперь он знал правду. У него счастливая миури - счастливая судьба. Он избранник богов. - В моих руках копия ключа Цифровой крепости, - послышался голос с американским акцентом.  - Не желаете купить. Нуматака чуть не расхохотался во весь голос.

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Top 12 Java Thread, Concurrency, and Multithreading Interview Questions For experienced Programmers

Ему предложили исчезнуть. - Диагностика, черт меня дери! - бормотал Чатрукьян, направляясь в свою лабораторию.

Эти изотопы нельзя разделить путем обычного химического извлечения. Кроме незначительной разницы в атомном весе, они абсолютно идентичны. - Атомный вес! - возбужденно воскликнул Джабба.  - Единственное различие - их атомный вес.

Чтобы ключ никто не нашел, Танкадо проделал то же самое с Цифровой крепостью. Он спрятал свой ключ, зашифровав его формулой, содержащейся в этом ключе. - А что за файл в ТРАНСТЕКСТЕ? - спросила Сьюзан. - Я, как и все прочие, скачал его с сайта Танкадо в Интернете. АНБ является счастливым обладателем алгоритма Цифровой крепости, просто мы не в состоянии его открыть.

Interview Questions on MultiThreading

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