3- Executors

Jul 03, 2026 22:57 · 6:50 · English · Whisper Turbo · 2 Kelliema

Din it-tranżazzjoni tiskadi llum. Aġġornament għall-ħażna permanenti →

Indiċi tal-Preżentazzjoni

0:03

S… Speaker 2 (3- Executors)

In Java,

0:04

S… Speaker 1 (3- Executors)

the concept of a thread pool is represented using the executor service interface

0:08

S… Speaker 1 (3- Executors)

and its implementations.

0:10

S… Speaker 1 (3- Executors)

So we have thread pool executor,

0:12

S… Speaker 1 (3- Executors)

which is a typical thread pool implementation.

0:15

S… Speaker 1 (3- Executors)

This is the one that we use most of the time.

0:17

S… Speaker 1 (3- Executors)

We also have scheduled thread pool executor.

0:20

S… Speaker 1 (3- Executors)

With this,

0:21

S… Speaker 1 (3- Executors)

we can schedule tasks to run after a delay or periodically.

0:24

S… Speaker 1 (3- Executors)

For example,

0:26

S… Speaker 1 (3- Executors)

we can schedule a task to run five hours from now or every two hours.

0:29

S… Speaker 1 (3- Executors)

We also have fork join pool.

0:33

S… Speaker 1 (3- Executors)

This is a special type of pool that is designed to recursively split a task

0:37

S… Speaker 1 (3- Executors)

into smaller tasks and then combine the results of each subtask to

0:41

S… Speaker 1 (3- Executors)

produce the overall result.

0:43

S… Speaker 1 (3- Executors)

It's like a divide and conquer algorithm.

0:46

S… Speaker 1 (3- Executors)

Now let me show you how to create a thread pool.

0:48

S… Speaker 1 (3- Executors)

We have this executors class that is declared in the java

0:52

S… Speaker 1 (3- Executors)

.util .concurrent package.

0:53

S… Speaker 1 (3- Executors)

This class has a bunch of static factory methods for creating

0:58

S… Speaker 1 (3- Executors)

an executor service.

0:59

S… Speaker 1 (3- Executors)

So with these methods we can create an instance of these implementations.

1:03

S… Speaker 1 (3- Executors)

Now, why shouldn't we create a new instance of thread pool executor

1:08

S… Speaker 1 (3- Executors)

directly?

1:08

S… Speaker 1 (3- Executors)

We can definitely do that,

1:09

S… Speaker 1 (3- Executors)

but it's a little bit difficult.

1:10

S… Speaker 2 (3- Executors)

Let me show you.

1:11

S… Speaker 1 (3- Executors)

So if you type new thread pool executor,

1:16

S… Speaker 2 (3- Executors)

take a look.

1:17

S… Speaker 1 (3- Executors)

This constructor has a bunch of parameters like core pool size,

1:21

S… Speaker 1 (3- Executors)

maximum pool size,

1:23

S… Speaker 1 (3- Executors)

keep a lifetime,

1:24

S… Speaker 2 (3- Executors)

and so on.

1:24

S… Speaker 1 (3- Executors)

So creating an executor explicitly is a little bit difficult.

1:28

S… Speaker 1 (3- Executors)

That is why we use the factory methods on the executors class.

1:33

S… Speaker 1 (3- Executors)

So here we can call new single thread executor.

1:36

S… Speaker 1 (3- Executors)

This returns an executor with a single thread.

1:38

S… Speaker 1 (3- Executors)

That's something that we use that often.

1:40

S… Speaker 1 (3- Executors)

We also have new fixed thread pool.

1:43

S… Speaker 1 (3- Executors)

This will create a thread pool with a given number of worker threads.

1:46

S… Speaker 1 (3- Executors)

So that would be an instance of the thread pool executor

1:51

S… Speaker 1 (3- Executors)

class.

1:51

S… Speaker 1 (3- Executors)

We also have new schedule thread pool.

1:54

S… Speaker 1 (3- Executors)

This will return

1:56

S… Speaker 1 (3- Executors)

instance of the scheduled thread pool executor.

1:59

S… Speaker 1 (3- Executors)

Okay, so let's call new fixed thread pool

2:03

S… Speaker 1 (3- Executors)

with two worker threads.

2:05

S… Speaker 1 (3- Executors)

Now we have stored a result in a variable called executor.

2:09

S… Speaker 1 (3- Executors)

Now look at the type of this variable.

2:11

S… Speaker 1 (3- Executors)

That is executor service.

2:14

S… Speaker 1 (3- Executors)

So we're dealing with an interface here.

2:15

S… Speaker 1 (3- Executors)

At runtime,

2:17

S… Speaker 1 (3- Executors)

the type of this object is going to be thread pool executor.

2:20

S… Speaker 2 (3- Executors)

Let me show you.

2:21

S… Speaker 1 (3- Executors)

So if you print executor

2:25

S… Speaker 1 (3- Executors)

.git class

2:27

S… Speaker 1 (3- Executors)

but get name and run the program we see

2:31

S… Speaker 1 (3- Executors)

thread pool executor that is a thread pool with a number of worker threats.

2:35

S… Speaker 1 (3- Executors)

Okay, so we have an executor

2:40

S… Speaker 1 (3- Executors)

now we can call executor .submit

2:44

S… Speaker 1 (3- Executors)

to submit a task to this thread pool.

2:46

S… Speaker 1 (3- Executors)

Now this method is overloaded.

2:48

S… Speaker 1 (3- Executors)

We can pass a runnable object.

2:50

S… Speaker 1 (3- Executors)

We can also pass a callable.

2:52

S… Speaker 1 (3- Executors)

That is a task that returns a result.

2:54

S… Speaker 1 (3- Executors)

We'll look at that later.

2:55

S… Speaker 1 (3- Executors)

So for now,

2:56

S… Speaker 1 (3- Executors)

let's pass a runnable object here.

2:58

S… Speaker 1 (3- Executors)

I'm going to use a lambda expression.

3:01

S… Speaker 1 (3- Executors)

So here,

3:02

S… Speaker 1 (3- Executors)

let's print the name of the current thread.

3:05

S… Speaker 1 (3- Executors)

So thread .currentThread .getName

3:10

S… Speaker 1 (3- Executors)

Now technically we don't need the braces here because we have a single print line statement,

3:14

S… Speaker 1 (3- Executors)

but I'm going to keep them here for clarity because I don't want to put this line over

3:19

S… Speaker 1 (3- Executors)

here, otherwise it's going to pop out of the screen.

3:21

S… Speaker 1 (3- Executors)

So that's all we have to do to run a task on a separate

3:25

S… Speaker 1 (3- Executors)

thread.

3:26

S… Speaker 1 (3- Executors)

If you run this program,

3:27

S… Speaker 1 (3- Executors)

you can see our task was executed on this

3:31

S… Speaker 1 (3- Executors)

thread. Pool one,

3:32

S… Speaker 1 (3- Executors)

thread one.

3:33

S… Speaker 1 (3- Executors)

So we didn't have to explicitly create a thread.

3:36

S… Speaker 1 (3- Executors)

Now if you have a thousand tasks,

3:38

S… Speaker 1 (3- Executors)

we don't have to worry about creating too many threads and running out of memory.

3:42

S… Speaker 1 (3- Executors)

We simply submit those tasks to this executor,

3:45

S… Speaker 2 (3- Executors)

to this thread pool,

3:46

S… Speaker 1 (3- Executors)

and this pool will assign our tasks to work your threads.

3:49

S… Speaker 2 (3- Executors)

Let me show you.

3:50

S… Speaker 1 (3- Executors)

So here we have a pool with two threads.

3:52

S… Speaker 1 (3- Executors)

Let's add a for loop for i,

3:56

S… Speaker 1 (3- Executors)

we start from 0 to let's say 10.

3:58

S… Speaker 1 (3- Executors)

Now in each iteration we submit

4:03

S… Speaker 1 (3- Executors)

a task to this pool.

4:04

S… Speaker 1 (3- Executors)

So we have only two threads available,

4:06

S… Speaker 1 (3- Executors)

but we're submitting 10 tasks.

4:08

S… Speaker 1 (3- Executors)

Let's see what happens.

4:09

S… Speaker 2 (3- Executors)

Take a

4:13

S… Speaker 2 (3- Executors)

look. So,

4:14

S… Speaker 1 (3- Executors)

some tasks are being executed on thread one,

4:16

S… Speaker 1 (3- Executors)

other tasks are being executed on thread two.

4:19

S… Speaker 2 (3- Executors)

See?

4:20

S… Speaker 1 (3- Executors)

So internally this executor maintains a queue.

4:23

S… Speaker 1 (3- Executors)

Every task that we submit goes in this queue and waits for an available

4:27

S… Speaker 1 (3- Executors)

thread.

4:28

S… Speaker 2 (3- Executors)

Okay?

4:28

S… Speaker 1 (3- Executors)

Now, let's get rid of this for loop.

4:30

S… Speaker 1 (3- Executors)

We don't need it anymore.

4:32

S… Speaker 1 (3- Executors)

So we create an executor and submit a task.

4:36

S… Speaker 1 (3- Executors)

Now, if I run this program again,

4:38

S… Speaker 1 (3- Executors)

we get this dialog box saying that our program is still running.

4:41

S… Speaker 1 (3- Executors)

Why is that?

4:42

S… Speaker 1 (3- Executors)

Because when we start an executor and submit a task,

4:45

S… Speaker 1 (3- Executors)

the executor thinks there might be more tasks coming in the future.

4:49

S… Speaker 1 (3- Executors)

So it's not going to terminate.

4:51

S… Speaker 1 (3- Executors)

It's going to stay in the memory waiting for new tasks.

4:53

S… Speaker 1 (3- Executors)

So we have to explicitly shut down an executor to terminate

4:58

S… Speaker 2 (3- Executors)

our program.

4:58

S… Speaker 1 (3- Executors)

And to do that we call executor .shutdown.

5:02

S… Speaker 1 (3- Executors)

We also have shutdown now.

5:04

S… Speaker 1 (3- Executors)

The difference is that the shutdown method doesn't stop the current tasks.

5:08

S… Speaker 1 (3- Executors)

So it will wait for the completion of those tasks,

5:11

S… Speaker 1 (3- Executors)

but it's not going to accept any new tasks.

5:13

S… Speaker 1 (3- Executors)

In contrast,

5:14

S… Speaker 1 (3- Executors)

if you call shutdown now,

5:16

S… Speaker 1 (3- Executors)

this will force the existing tasks to stop.

5:18

S… Speaker 1 (3- Executors)

Okay, so let's call the shutdown method.

5:22

S… Speaker 1 (3- Executors)

Now we run the program.

5:23

S… Speaker 1 (3- Executors)

We get this dialog box because we didn't shut down our executor previously.

5:27

S… Speaker 1 (3- Executors)

So let's rerun this program.

5:31

S… Speaker 1 (3- Executors)

All right, our program shut down.

5:32

S… Speaker 1 (3- Executors)

So if I run it again,

5:34

S… Speaker 1 (3- Executors)

we don't get that warning.

5:35

S… Speaker 1 (3- Executors)

Okay.

5:35

S… Speaker 2 (3- Executors)

Now,

5:36

S… Speaker 1 (3- Executors)

what if something goes wrong over here?

5:41

S… Speaker 1 (3- Executors)

Or we might have some code and

5:45

S… Speaker 1 (3- Executors)

this code throws an exception.

5:47

S… Speaker 1 (3- Executors)

With that,

5:48

S… Speaker 1 (3- Executors)

we're not going to be able to shut down an executor properly.

5:51

S… Speaker 1 (3- Executors)

So as a best practice,

5:53

S… Speaker 1 (3- Executors)

we should run this inside a try find block.

5:56

S… Speaker 1 (3- Executors)

So I'm going to add a try block here and the

6:00

S… Speaker 1 (3- Executors)

try block

6:01

S… Speaker 1 (3- Executors)

we submit our task and in

6:05

S… Speaker 1 (3- Executors)

the final block,

6:06

S… Speaker 1 (3- Executors)

we shut down the executor.

6:10

S… Speaker 1 (3- Executors)

With this,

6:11

S… Speaker 1 (3- Executors)

we'll make sure that no matter what,

6:13

S… Speaker 1 (3- Executors)

we always shut down an executor and release it from the memory.

6:18

S… Speaker 1 (3- Executors)

So this is the benefit of using the executor framework.

6:20

S… Speaker 1 (3- Executors)

We don't have to worry about threat manipulation anymore.

6:23

S… Speaker 1 (3- Executors)

We let Java,

6:24

S… Speaker 1 (3- Executors)

we let the executor framework take care of all of that.

6:26

S… Speaker 1 (3- Executors)

But you have to remember,

6:28

S… Speaker 1 (3- Executors)

even when using the executor framework,

6:30

S… Speaker 1 (3- Executors)

we still have to worry about the concurrency problems.

6:32

S… Speaker 1 (3- Executors)

So if two tasks modify an object

6:36

S… Speaker 1 (3- Executors)

concurrently, we're going to run into issues.

6:38

S… Speaker 1 (3- Executors)

So the executor framework does not protect us from the concurrency problems

6:42

S… Speaker 1 (3- Executors)

we talked about in the last section.

6:44

S… Speaker 1 (3- Executors)

It just simplifies threat manipulation.

Din it-tranżmissjoni ġiet iġġenerata minn AI (rikonoxximent awtomatiku tad-diskors) jista' jkun fiha żbalji — ivverifika mal-awdjo oriġinali għal użu kritiku. Politika dwar l-AI

❤️ Imħabba STT.ai? Għid lill-ħbieb tiegħek!

Sommarju

Ikklikkja Sommarju biex tiġġenera sommarju AI ta ’dan it-traskrizzjoni.

Staqsi AI Dwar Dan Tranżkript

Staqsi xi ħaġa dwar din it-traskrizzjoni — l-AI se ssib sezzjonijiet rilevanti u twieġeb.

Traskrizzjoni ieħor