27 - Multithreading/001 Multithreading Overview_en.srt

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Hello, yes, students today will start learning a new topic, Moonface Riden, this is huge topic,

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and after this course, you will have a lot of knowledge that you can apply in different programming

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languages to support not just execution, but in scope of this course.

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I will show you how MultiThreaded works on Java examples and take into account this is the first lesson

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of new topic, this lesson a little bit more theoretical one to be sure that we have enough high level

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knowledge and understanding before we'll start sharing, quote, examples in the next lesson.

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That's why today we'll focus our attention on such questions as what is the process in our computers?

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What is the threat of execution?

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What is multithreaded in programming also in this lesson and explain how multiscreen works and what

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threats and translation means.

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And the standard answers on these questions will bring us to the point where we can discuss with you

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why multiscreen is needed and what a benefit, something which is written.

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And also we'll discuss dark side of multithreaded to understand it, drawbacks and what we should always

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take into account while working as much as freedom.

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And the end of the lesson, I will give you an overview of what packages and tools we are going to learn

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in this course in JDK.

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Answering all these questions will give you insights on what we are going to learn in this course.

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I believe we are good with our agenda for today.

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Let's start and before we even start discussion of multithreaded in the program, let's understand what

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the process is in computer science.

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In simple words, process is an instance of a computer program.

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You opened a glimpse.

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It's a separate process to run as a Java program.

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Is that a separate Java process?

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Computer program is nothing more than a set of instructions for a machine but process.

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It is an execution of these instructions.

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A process has a self-contained execution environment.

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That means that each process has its own memory space.

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And as I said before, usually processes and programs are considered to be very close terms.

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But what end user interaction with may be a set of processes that interact with each other doing no

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such popular Internet browser as Google Chrome?

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So long to go home and look at the task manager.

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You will see separate processes for each stop in your browser.

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But for the end user, Manglehorn perceived like a single application.

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This is because most operating system support interpersonal communication resources, sap, pipes and

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sockets.

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These resources are used to interact between different processes, homes, and this is pretty straightforward.

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Now let's understand what threat of execution is.

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Each process may be executed in one or more threats of execution.

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In this case, our program is executed concurrently.

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In other words, some instructions are executed in parallel.

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In computer science, concurrency is a duplicate of different parts or units of a program algorithm

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or problem to be executed out of order or at the same time simultaneously without affecting the final

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outcome.

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So we can say that each process may be executed in multiple threats.

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In the learning literature, you might even find mention about different name of abstracts.

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Sometimes they're called as lightweight processes or threats, share process resources.

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This is something that may cause issues during the multithreaded.

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If you're allocated two gigabytes for a GBM, that means all created stress will work within these two

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gigabytes and we'll share in between each other.

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Knowing your memory will be allocated to threat of execution.

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I hope you already know the answer to my next question.

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What is a move to threaten?

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To threaten is the process of execution of program in multiple threats.

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Most of the operating systems nowadays support this feature.

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You have multiple course in your processa multithreaded allows you to use all course for execution of

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your program instructions.

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EPU executes one task at a time and we as the software engineers will write instructions how to split

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between different threats of execution.

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That's what we are going to learn.

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Let me explain it now.

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How multiscreen program works on the high level, you always have one threat of execution.

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One program just started.

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That is your main threat of execution.

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After that, you can run so-called child threats of execution and describe instructions what those threats

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should work on.

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In parallel, the different use cases of using Otis Redding.

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And we'll look at them in the minute.

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And now the important thing, how to synchronize the work of different threats imagines at your peril

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to your work between multiple threats.

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It is another thing that.

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All of the threats are part of one program, and sometimes threat needs to update on the man's threat

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about state of execution or result of execution.

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But sometimes threats also need to interact with each other, take into account all threats, working

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with some shared resource.

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To rephrase this in simple words, imagine that you have a collection of users and you need to filter

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this collection and remove users that have less than one thousand dollars total.

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Check in your online shop and you decided to split the task between different threats of execution.

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Each threat of execution works with shared resource collection of users.

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Each threat takes users from this common collection to provide the result of the specific part of namely

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users are equally distributed between different threats but all threats to removing users from the common

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collection shared between all of them.

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Can you understand what the shared resource mean on this example?

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Let's review also other use cases of multithreaded programming and the one we might want to use this

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approach.

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I believe that we have already discussed the first case.

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That is the case when different threats on these slides are marked with capital key and numbers reaching

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out to shared resource that is marked with capital are in this case to modify the state of the resource.

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So next year's case of using multithreaded is reading and writing operations.

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You know that in Java, most of the input output streams, blogs and in process of execution.

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So why don't we use features of malicious reading?

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And in case we need to write, let's say, some file, we do this in a separate thread.

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For example, a user asked us to do an expert of all users to see format and wants to download this

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info.

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No problem at all.

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We are writing a separate threat of execution and other parts of our program proceed, working without

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any free's user still able to click on other buttons and perform other operations while file downloading

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is in progress.

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Is that clear?

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Same situation with redundant info.

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Let's create a separate threat of execution that will show a status of uploading, and once uploading

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is finished, we will be notified about that fact and we'll proceed from there.

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Pay attention to how your clips is working when your important project or performance some other operations.

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Eclipse is also Java application was multithreaded feature inside.

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When any operation is performed, UI is not completely blocked and you still can perform as operations

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with the clips in parallel.

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The third case is a case when once to produce some data and other thread consumes this data.

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These threads are working independently and potentially may interact with the help of the queue between

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each other.

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On the slide here you can see that we have producer and consumer producer send some item ready for processing

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to the queue and consumer take this item from the queue when ready to process the next item.

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The next case is a typical scenario with writers and readers.

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Imagine that you have some shared resource, some shared buffer, and from one side you have writers

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that might be separate services.

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Read that, write some information to the buffer.

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It can be is a strong representation of new objects or requests to the app.

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Literally everything.

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And on the other side, you have readers that read data from the buffer.

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This example is different from all previous ones that we have discussed because here we have some specific

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conditions on the ones that can write to the buffer at the point of time readers can to read during

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the writing, all the readers may read data simultaneously, will have similar tasks in this course.

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And I will show you how to solve this task.

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Really interesting, don't you think so?

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Probably these are the most popular use cases of using an Otis Redding approach.

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Definitely there will be variations of these use cases and sometimes even different scenarios, but

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we'll try to cover as much as we can on this course.

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Now let's discuss advantages and disadvantages of multi threading approach.

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Let's start from advantages of multithreaded.

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It was to name a few important ones.

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They are effective use of multiple course of your processa, high performance of your program during

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execution of specific operations and data processing.

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Good to use with operations that block mansard of execution.

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Like I said before, in case of working with input output streams, application responsiveness, if

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there is a need to perform, some operation application won't be frozen until that operation is completed.

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Instead, I will execute request in a separate thread.

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Probably these are main advantages of using these advantages, maintaining the Australian approach.

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Across all over the world and in different programming languages, but there are always two sides of

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a metal, all these advantages come with a group of disadvantages.

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Some of them are it is easy to use is written incorrectly by saying this, I would like to highlight

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that using what is right.

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And it requires a good understanding of the toolset to implement concurrent execution of your program.

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And that is relatively easy to do.

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A mistake, for example, in synchronous court, sometimes also of execution doesn't play a big role.

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Or you can write code in different ways with the thread and it is not so easy and straightforward.

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You need to be sure about what pieces of code you need to synchronize between different threads, how

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much stress you need, how to split work between threads and so on.

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Incorrect and suitable usage of Montasser in May cause your performance.

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You need to understand that multithreaded works perfectly, not for all tasks.

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For example, you might not always see the benefit of using what is written while working with small

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data in case you want to implement a certain approach and filter an election was one hundred integers.

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More likely, it will take more time than performing the same operation synchronously in one step.

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Why?

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Because running threads, synchronization time, corporatization of different threads on different CPUs.

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All of this takes time and we need to be sure that when we apply to certain approach, it is really

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worth it and we will benefit from this and some mistakes even can bring it to the deadlock and lifework

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cases.

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When your program doesn't perform any useful activity, hard to debark application and find the mistake,

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it is much harder to replicate an error in the multithreaded application than it is to do so in a single

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threaded application.

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As a result, it is more difficult to identify and verify root causes when error.

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Secure testing process of multithreaded app is more difficult.

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Testing the multithreaded application is more difficult than testing a single application because the

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effects are often timing related and more difficult to reproduce.

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It is difficult to introduce notice writing approach already created code because all code needs to

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be analyzed by engineers, static variables, methods and locations and critical areas.

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Everything needs to be reviewed and adjusted to make sure that the implementation of concurrent programming

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approach will not affect all application.

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The main disadvantages of multithreaded that we also need to consider when we want to create scalable

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app with high performance.

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In this course, we are going to learn tools for concurrent programming most tools, classes and interfaces

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allocated in Java.

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You can current package.

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This package also has some set packages, also some main types like Runnable and Thread located in general

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and package.

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But most of the classes and interfaces, including concurrent collections, locks and other mechanisms

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for stress synchronization executer services and most of the things that we are going to learn allocated

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individual concurrent package.

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We have really a lot of interesting things to learn.

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Now let's recap what we have learned in this lesson and this lesson.

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We learned what the process is and what the threat is.

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We also learned what is a multiscreen program programming now, you know, the most popular use cases

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of not just training programs.

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We learned advantages and disadvantages of concurrent programming.

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That's all for this lesson.

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Looking forward to seeing you in the next lesson.