13- Combining Completable Futures

Jul 04, 2026 01:15 · 4:32 · English · Whisper Turbo · 1 Speakers

Henda útgávan er útgivin í dag. Uppgradering til permanent lagring →

Lærarabókin

0:03

S… Speaker 1 (13- Combining Completable Futures)

In my opinion,

0:04

S… Speaker 1 (13- Combining Completable Futures)

one of the most powerful features of completable futures is the ability

0:08

S… Speaker 1 (13- Combining Completable Futures)

to start two tasks asynchronously and then combine the results.

0:13

S… Speaker 1 (13- Combining Completable Futures)

For example,

0:13

S… Speaker 1 (13- Combining Completable Futures)

let's say we call a remote service to get the price of a

0:17

S… Speaker 1 (13- Combining Completable Futures)

product and that service returns the price in US dollars.

0:21

S… Speaker 1 (13- Combining Completable Futures)

So we get 20 US dollars.

0:23

S… Speaker 1 (13- Combining Completable Futures)

Now at the same time,

0:25

S… Speaker 1 (13- Combining Completable Futures)

in parallel,

0:26

S… Speaker 1 (13- Combining Completable Futures)

we want to call another service to get the exchange rate between US

0:30

S… Speaker 1 (13- Combining Completable Futures)

dollars and euros.

0:32

S… Speaker 1 (13- Combining Completable Futures)

So that service is going to return 0 .9.

0:34

S… Speaker 1 (13- Combining Completable Futures)

Now we don't want to call the second service upon completion of the first

0:38

S… Speaker 1 (13- Combining Completable Futures)

task.

0:38

S… Speaker 1 (13- Combining Completable Futures)

We want to start this task concurrently and then wait for both of them to complete

0:43

S… Speaker 1 (13- Combining Completable Futures)

in order to calculate the result.

0:45

S… Speaker 1 (13- Combining Completable Futures)

So let me show you how to do this.

0:47

S… Speaker 1 (13- Combining Completable Futures)

First we want to create a completable future to return the price of

0:51

S… Speaker 1 (13- Combining Completable Futures)

a product.

0:51

S… Speaker 1 (13- Combining Completable Futures)

So completable future .supply async and

0:56

S… Speaker 1 (13- Combining Completable Futures)

here we return 20.

0:57

S… Speaker 1 (13- Combining Completable Futures)

That is our first task.

1:01

S… Speaker 1 (13- Combining Completable Futures)

Now, in our second task,

1:02

S… Speaker 1 (13- Combining Completable Futures)

we're going to call another service to get the exchange rate between US

1:06

S… Speaker 1 (13- Combining Completable Futures)

dollars and euros.

1:07

S… Speaker 1 (13- Combining Completable Futures)

So one more time,

1:08

S… Speaker 1 (13- Combining Completable Futures)

completable future,

1:10

S… Speaker 1 (13- Combining Completable Futures)

dot supply async,

1:11

S… Speaker 1 (13- Combining Completable Futures)

here we return 0 .9.

1:14

S… Speaker 1 (13- Combining Completable Futures)

This is our second task.

1:16

S… Speaker 1 (13- Combining Completable Futures)

Now we call first dot then combine.

1:22

S… Speaker 1 (13- Combining Completable Futures)

With this we can combine the result of two asynchronous operations.

1:26

S… Speaker 1 (13- Combining Completable Futures)

So we can wait for both of them to complete to calculate the final result.

1:30

S… Speaker 1 (13- Combining Completable Futures)

But here's the interesting part.

1:32

S… Speaker 1 (13- Combining Completable Futures)

Calling this method is not going to block the current thread.

1:35

S… Speaker 1 (13- Combining Completable Futures)

We're basically building a processing pipeline.

1:38

S… Speaker 1 (13- Combining Completable Futures)

We're building a recipe.

1:39

S… Speaker 1 (13- Combining Completable Futures)

We're telling the executor framework,

1:41

S… Speaker 1 (13- Combining Completable Futures)

hey, go ahead and start these two tasks concurrently.

1:45

S… Speaker 1 (13- Combining Completable Futures)

When they're both complete,

1:46

S… Speaker 1 (13- Combining Completable Futures)

start a new task to do something else.

1:49

S… Speaker 1 (13- Combining Completable Futures)

All of this is happening asynchronously,

1:51

S… Speaker 1 (13- Combining Completable Futures)

okay?

1:52

S… Speaker 1 (13- Combining Completable Futures)

So look at the signature of this method.

1:54

S… Speaker 1 (13- Combining Completable Futures)

Here we have two parameters.

1:56

S… Speaker 1 (13- Combining Completable Futures)

The first parameter is a completion stage object.

2:00

S… Speaker 1 (13- Combining Completable Futures)

That is our second task.

2:01

S… Speaker 1 (13- Combining Completable Futures)

So let's pass it over here.

2:03

S… Speaker 1 (13- Combining Completable Futures)

Now the second parameter is a bifunction.

2:06

S… Speaker 1 (13- Combining Completable Futures)

That is a function with two parameters that returns a value.

2:10

S… Speaker 1 (13- Combining Completable Futures)

Look at the type of these parameters.

2:12

S… Speaker 1 (13- Combining Completable Futures)

The first parameter is an integer.

2:14

S… Speaker 1 (13- Combining Completable Futures)

The second is a double.

2:16

S… Speaker 1 (13- Combining Completable Futures)

So these parameters represent the results of

2:20

S… Speaker 1 (13- Combining Completable Futures)

our tasks.

2:21

S… Speaker 1 (13- Combining Completable Futures)

So the first task returns a price in US dollars and

2:26

S… Speaker 1 (13- Combining Completable Futures)

the second task returns the exchange rate.

2:28

S… Speaker 1 (13- Combining Completable Futures)

Exchange rate.

2:31

S… Speaker 1 (13- Combining Completable Futures)

So this is our buy function.

2:32

S… Speaker 1 (13- Combining Completable Futures)

Now we get these two values and based on these we're going to calculate

2:37

S… Speaker 1 (13- Combining Completable Futures)

a new value.

2:38

S… Speaker 1 (13- Combining Completable Futures)

So here we can return price times exchange rate.

2:42

S… Speaker 1 (13- Combining Completable Futures)

Okay?

2:43

S… Speaker 1 (13- Combining Completable Futures)

Now,

2:44

S… Speaker 1 (13- Combining Completable Futures)

this method

2:45

S… Speaker 1 (13- Combining Completable Futures)

Then combine is going to return a new completable future.

2:49

S… Speaker 1 (13- Combining Completable Futures)

So after that we can call then accept.

2:53

S… Speaker 1 (13- Combining Completable Futures)

Here we get the result and print it.

2:56

S… Speaker 1 (13- Combining Completable Futures)

Now let's reformat our code.

3:00

S… Speaker 1 (13- Combining Completable Futures)

That is better.

3:02

S… Speaker 1 (13- Combining Completable Futures)

So run.

3:04

S… Speaker 1 (13- Combining Completable Futures)

So the price is $18.

3:07

S… Speaker 1 (13- Combining Completable Futures)

Now let's make this example more interesting.

3:10

S… Speaker 1 (13- Combining Completable Futures)

Let's imagine that the first task returns the price as

3:14

S… Speaker 1 (13- Combining Completable Futures)

a string.

3:15

S… Speaker 1 (13- Combining Completable Futures)

20 US dollars.

3:18

S… Speaker 1 (13- Combining Completable Futures)

Now we have a compilation error because we cannot multiply a string by

3:22

S… Speaker 1 (13- Combining Completable Futures)

a number.

3:23

S… Speaker 1 (13- Combining Completable Futures)

So in our first task,

3:25

S… Speaker 1 (13- Combining Completable Futures)

we should transform the result.

3:27

S… Speaker 1 (13- Combining Completable Futures)

So right after calling the supply async method,

3:30

S… Speaker 1 (13- Combining Completable Futures)

we call then apply.

3:33

S… Speaker 1 (13- Combining Completable Futures)

Here we should pass a function that takes a string and returns a

3:37

S… Speaker 1 (13- Combining Completable Futures)

new value, in this case an integer.

3:39

S… Speaker 1 (13- Combining Completable Futures)

So I'm going to reformat this code.

3:42

S… Speaker 1 (13- Combining Completable Futures)

First we call supply async and then

3:46

S… Speaker 1 (13- Combining Completable Futures)

then apply.

3:47

S… Speaker 1 (13- Combining Completable Futures)

So here we get a string

3:51

S… Speaker 1 (13- Combining Completable Futures)

Now we call str .replace.

3:53

S… Speaker 1 (13- Combining Completable Futures)

I'm going to replace US dollars with an empty string.

3:58

S… Speaker 1 (13- Combining Completable Futures)

We could also use regular expressions.

4:00

S… Speaker 1 (13- Combining Completable Futures)

It doesn't really matter.

4:01

S… Speaker 1 (13- Combining Completable Futures)

This is a very basic transformation.

4:03

S… Speaker 1 (13- Combining Completable Futures)

So we get that.

4:04

S… Speaker 1 (13- Combining Completable Futures)

That gives us the price.

4:06

S… Speaker 1 (13- Combining Completable Futures)

Now we call integer .parseInt

4:10

S… Speaker 1 (13- Combining Completable Futures)

and pass the price.

4:12

S… Speaker 1 (13- Combining Completable Futures)

And finally return the result.

4:15

S… Speaker 1 (13- Combining Completable Futures)

So here's our first task.

4:17

S… Speaker 1 (13- Combining Completable Futures)

Then we have our second task.

4:18

S… Speaker 1 (13- Combining Completable Futures)

We combine them and wait for both of them to complete before

4:22

S… Speaker 1 (13- Combining Completable Futures)

displaying the result.

4:24

S… Speaker 1 (13- Combining Completable Futures)

Now all of this is happening asynchronously.

4:26

S… Speaker 1 (13- Combining Completable Futures)

So none of this code is going to block the current threat.

This transcript was generated by AI (automatic speech recognition). May contain errors - check against the original audio for critical use. Politikkur

❤️ Love STT.ai? Tell your friends!

Samandráttur

Click Summarize to generate an AI summary of this transcript.

Spørg AI um hetta transkriptión

Tað er ein spurningur um, hvussu nógvar ferðir ein kann skriva og lesa.

Transcribe otro