8- Implementing an Asynchronous API

Jul 03, 2026 23:07 · 4:18 · English · Whisper Turbo · 2 Wasemaji

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Index YA TAA

0:03

S… Speaker 1 (8- Implementing an Asynchronous API)

Let me show you how to create an asynchronous API.

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S… Speaker 1 (8- Implementing an Asynchronous API)

This is a very powerful technique that you should start using in your applications right

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S… Speaker 1 (8- Implementing an Asynchronous API)

away. So in this project,

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S… Speaker 1 (8- Implementing an Asynchronous API)

I'm going to add a new class mail service.

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S… Speaker 1 (8- Implementing an Asynchronous API)

We're going to use this class to send emails to our users.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Now,

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S… Speaker 1 (8- Implementing an Asynchronous API)

here we need a method like public void send.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Now in a real application,

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S… Speaker 1 (8- Implementing an Asynchronous API)

we should pass a mail message object,

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S… Speaker 1 (8- Implementing an Asynchronous API)

but let's not worry about that.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Instead,

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S… Speaker 1 (8- Implementing an Asynchronous API)

we're just going to print a message like mail was sent.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Now, sending an email is a long running operation because we have to go over

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S… Speaker 1 (8- Implementing an Asynchronous API)

the network.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Basically,

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S… Speaker 1 (8- Implementing an Asynchronous API)

anytime we have to touch the file system or the network,

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S… Speaker 1 (8- Implementing an Asynchronous API)

we're dealing with a long running operation.

0:45

S… Speaker 1 (8- Implementing an Asynchronous API)

And we shouldn't run these operations on the main thread.

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S… Speaker 1 (8- Implementing an Asynchronous API)

We should run them on a separate thread.

0:50

S… Speaker 1 (8- Implementing an Asynchronous API)

So to simulate a long running operation,

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S… Speaker 1 (8- Implementing an Asynchronous API)

I'm going to use our long task class that we created in the last section.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Here we call the simulate method,

0:59

S… Speaker 1 (8- Implementing an Asynchronous API)

which adds a three second delay to this method.

1:02

S… Speaker 1 (8- Implementing an Asynchronous API)

Okay.

1:02

S… Speaker 1 (8- Implementing an Asynchronous API)

Now,

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S… Speaker 1 (8- Implementing an Asynchronous API)

In our main method,

1:05

S… Speaker 1 (8- Implementing an Asynchronous API)

I'm going to create a new mail service

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S… Speaker 1 (8- Implementing an Asynchronous API)

and then call service .send.

1:12

S… Speaker 2 (8- Implementing an Asynchronous API)

Now,

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S… Speaker 1 (8- Implementing an Asynchronous API)

this is a synchronous or blocking operation.

1:16

S… Speaker 1 (8- Implementing an Asynchronous API)

So if we print another message here like hello world,

1:20

S… Speaker 1 (8- Implementing an Asynchronous API)

we're not going to see this until this method returns.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Let me show you.

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S… Speaker 1 (8- Implementing an Asynchronous API)

So run,

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S… Speaker 1 (8- Implementing an Asynchronous API)

you're waiting for the mail to be sent.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Three seconds later,

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S… Speaker 1 (8- Implementing an Asynchronous API)

the mail is sent and now we see the hello world message.

1:32

S… Speaker 1 (8- Implementing an Asynchronous API)

So this is the problem with synchronous or blocking code.

1:36

S… Speaker 2 (8- Implementing an Asynchronous API)

Now,

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S… Speaker 1 (8- Implementing an Asynchronous API)

anytime we have a long running operation like querying a database,

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S… Speaker 1 (8- Implementing an Asynchronous API)

calling a remote service,

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S… Speaker 1 (8- Implementing an Asynchronous API)

working with the file system,

1:43

S… Speaker 1 (8- Implementing an Asynchronous API)

we should run these operations asynchronously.

1:46

S… Speaker 1 (8- Implementing an Asynchronous API)

Let me show you how to do that.

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S… Speaker 1 (8- Implementing an Asynchronous API)

So we go back to our mail service class.

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S… Speaker 1 (8- Implementing an Asynchronous API)

I'm going to re -implement this method in an asynchronous fashion.

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S… Speaker 1 (8- Implementing an Asynchronous API)

So we add another method,

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S… Speaker 1 (8- Implementing an Asynchronous API)

public,

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S… Speaker 1 (8- Implementing an Asynchronous API)

instead of returning void,

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S… Speaker 1 (8- Implementing an Asynchronous API)

we're going to return a completable future of void.

2:02

S… Speaker 1 (8- Implementing an Asynchronous API)

If this method returned an integer here,

2:05

S… Speaker 1 (8- Implementing an Asynchronous API)

we would use completable future of integer.

2:07

S… Speaker 1 (8- Implementing an Asynchronous API)

Okay.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Now we call this method send async.

2:11

S… Speaker 1 (8- Implementing an Asynchronous API)

So by convention,

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S… Speaker 1 (8- Implementing an Asynchronous API)

we add the async suffix to this method.

2:15

S… Speaker 1 (8- Implementing an Asynchronous API)

Okay.

2:15

S… Speaker 1 (8- Implementing an Asynchronous API)

Now here we should return a completable future object.

2:20

S… Speaker 1 (8- Implementing an Asynchronous API)

You learned how to do that in the last video.

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S… Speaker 1 (8- Implementing an Asynchronous API)

So we return completable future because

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S… Speaker 1 (8- Implementing an Asynchronous API)

we're not going to return a value.

2:27

S… Speaker 1 (8- Implementing an Asynchronous API)

We should call the run async method.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Now here we should pass a runnable object.

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S… Speaker 1 (8- Implementing an Asynchronous API)

So we use a lambda and in the body of this lambda

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S… Speaker 1 (8- Implementing an Asynchronous API)

we simply call our synchronous method as simple

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S… Speaker 1 (8- Implementing an Asynchronous API)

as that.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Now with this single line of code we can execute this method in

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S… Speaker 1 (8- Implementing an Asynchronous API)

an asynchronous fashion because when we call the run async method

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S… Speaker 1 (8- Implementing an Asynchronous API)

the task that we pass here is going to be executed on a separate thread

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S… Speaker 1 (8- Implementing an Asynchronous API)

on the common thread pool.

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S… Speaker 1 (8- Implementing an Asynchronous API)

So if you have an existing synchronous method,

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S… Speaker 1 (8- Implementing an Asynchronous API)

you can simply convert it to an asynchronous method by wrapping it inside

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S… Speaker 1 (8- Implementing an Asynchronous API)

a completable future object.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Now,

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S… Speaker 1 (8- Implementing an Asynchronous API)

back to our main method.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Here we call send async.

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S… Speaker 2 (8- Implementing an Asynchronous API)

Now,

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S… Speaker 1 (8- Implementing an Asynchronous API)

because this is an asynchronous method,

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S… Speaker 1 (8- Implementing an Asynchronous API)

it's not going to block the current thread.

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S… Speaker 1 (8- Implementing an Asynchronous API)

So the moment I run this program,

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S… Speaker 1 (8- Implementing an Asynchronous API)

we're going to see this hello world message immediately.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Then we wait three seconds for the mail to be sent.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Take a look.

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S… Speaker 1 (8- Implementing an Asynchronous API)

So run

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S… Speaker 1 (8- Implementing an Asynchronous API)

We see the hello world message,

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S… Speaker 1 (8- Implementing an Asynchronous API)

but what happened to our mail?

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S… Speaker 1 (8- Implementing an Asynchronous API)

Well,

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S… Speaker 1 (8- Implementing an Asynchronous API)

here we have a command line program and this program terminated so quickly

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S… Speaker 1 (8- Implementing an Asynchronous API)

that we didn't see the result of this task that was executed on a separate thread.

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S… Speaker 1 (8- Implementing an Asynchronous API)

We don't have this problem in a mobile or a desktop app because these apps

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S… Speaker 1 (8- Implementing an Asynchronous API)

are continuously running until the user terminates them.

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S… Speaker 1 (8- Implementing an Asynchronous API)

So to prove to you that our mail was being sent on a separate thread,

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S… Speaker 1 (8- Implementing an Asynchronous API)

I'm going to put a delay over here.

3:49

S… Speaker 1 (8- Implementing an Asynchronous API)

Let's say thread that sleep for five seconds.

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S… Speaker 1 (8- Implementing an Asynchronous API)

we should wrap this in a try catch block.

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S… Speaker 1 (8- Implementing an Asynchronous API)

Now we run our program so we

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S… Speaker 1 (8- Implementing an Asynchronous API)

see the hello world message three seconds later the mail was sent and then two seconds

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S… Speaker 1 (8- Implementing an Asynchronous API)

later our program finished.

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S… Speaker 1 (8- Implementing an Asynchronous API)

So this is the benefit of asynchronous API's they

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S… Speaker 1 (8- Implementing an Asynchronous API)

don't block the current thread and allow us to better exploit our parallel

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S… Speaker 1 (8- Implementing an Asynchronous API)

hardware.

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