ntflix / async_tests

async tests

This is a simple example of using async in Java.

Output

Calculating factorial of 5...
This is some code that comes after the async call!! :D
Magic!
Factorial of 5 is 120
This is some code that comes after the main thread sleep!!

Explanation

The async keyword is used to mark a method as asynchronous. This means that the method will be executed in a separate thread. The method must return a CompletableFuture object. The CompletableFuture object is used to get the result of the asynchronous method.

The CompletableFuture object has a method called get() which will block the current thread until the result is available. This is why we have to call get() on the CompletableFuture object in the main method.

Code

import java.util.concurrent.CompletableFuture;

public class AsyncTest {
    public static void main(String[] args) throws Exception {
        System.out.println("Calculating factorial of 5...");
        CompletableFuture<Integer> future = factorial(5);
        System.out.println("This is some code that comes after the async call!! :D");
        System.out.println("Magic!");
        System.out.println("Factorial of 5 is " + future.get());
    }

    public static CompletableFuture<Integer> factorial(int n) {
        return CompletableFuture.supplyAsync(() -> {
            int result = 1;
            for (int i = 1; i <= n; i++) {
                result *= i;
            }
            return result;
        });
    }
}