How to execute a callable in the executor service

submit() is an instance method that takes a callable task as a parameter for execution and returns a Future.

Refer to What is the difference between runnable and callable in Java? to understand more about Callable in Java.

Syntax

<T> Future<T> submit(Callable<T> task)

Parameters

  • Callable<T> task: The callable task to execute.

Return value

This method returns a Future.

Code

import java.util.concurrent.*;
public class Main {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        ExecutorService executorService = Executors.newSingleThreadExecutor();
        Callable<String> stringCallable = () -> "Callable called";
        Future<String> callableFuture = executorService.submit(stringCallable);
        System.out.println("Result of the callable - " + callableFuture.get());
        executorService.shutdown();
    }
}

Explanation

  • Line 1: We import the relevant packages.
  • Line 6: We define a single-threaded executor service called executorService.
  • Line 8: We define a callable called stringCallable that returns a string value.
  • Line 10: We submit the stringCallable to the executorService using the submit() method. The submit() method returns a Future.
  • Line 12: We retrieve the value of the Future obtained in line 10 using the get() method and print the result. (To learn more about the Future.get() method in Java, read this shot.)

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