How to get asynchronous task's result with timeout in Java

Syntax

V get(long timeout, TimeUnit unit)

Parameters

long timeout: The maximum amount of time to wait.
TimeUnit unit: The unit of time.

Return value

This method returns the result of the computation.

Code

import java.util.concurrent.*;
public class Main {
    private static String process(){
        sleep(2000);
        System.out.println("Current Execution thread where the supplier is executed - " + Thread.currentThread().getName());
        return "Hello Educative";
    }
    private static CompletableFuture<String> createFuture(){
        return CompletableFuture.supplyAsync(Main::process);
    }
    private static void sleep(int millis){
        try {
            Thread.sleep(millis);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    public static void main(String[] args) throws ExecutionException, InterruptedException, TimeoutException {
        CompletableFuture<String> stringCompletableFuture = createFuture();
        long timeOutValue = 1;
        TimeUnit timeUnitForTimeOut = TimeUnit.SECONDS;
        String value = stringCompletableFuture.get(timeOutValue, timeUnitForTimeOut);
        sleep(2000);
        System.out.println("Completed Processing. Returned value - " + value);
    }
}

Explanation

Line 1: We import the relevant packages and classes.
Lines 6-10: We define a function called process that prints the thread executing the function, sleeps for one second, and returns a string.
Lines 12-14: We define a function called createFuture. This function uses the supplyAsync() method to run the process() method in the common pool of ForkJoinPool. The function returns a CompletableFuture.
Lines 16-22: We define a function called sleep() that makes the current thread sleep for the given amount of milliseconds.
Line 25: We get the CompletableFuture by invoking the createFuture method.
Line 27: We define the wait time value as timeOutValue.
Line 29: We define the wait time unit as timeUnitForTimeOut.
Line 31: We try to retrieve the value returned by the supplier function process using the get method. We pass the timeOutValue and timeUnitForTimeOut as arguments to the get() method.
Line 33: We invoke the sleep function on the main thread.
Line 35: We print the value returned by the get() method.

When the code above is run, the code throws a TimeoutException that indicates the task took more time to complete than the wait time period.

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)

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