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What is Callable?

Deepika Sahu answered on December 15, 2022 Popularity 9/10 Helpfulness 1/10

answer What is Callable?

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What is Callable?

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 Callable is an interface with single abstract method call().
    Java 5 introduced java.util.concurrent.Callable interface in concurrency package
    that is similar to Runnable interface but it can return any Object and is able to throw Exception.
    Callable interface use Generic to define the return type of Object.

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Contributed on Dec 15 2022

Deepika Sahu

0 Answers Avg Quality 2/10

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What is Callable?

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Callable is an interface with single abstract method call().

Java 5 introduced java.util.concurrent.Callable interface in concurrency package

that is similar to Runnable interface but it can return any Object and is able to throw Exception.

Callable interface use Generic to define the return type of Object.

package com.journaldev.threads;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class MyCallable implements Callable<String> {

    @Override
    public String call() throws Exception {
        Thread.sleep(1000);
        //return the thread name executing this callable task
        return Thread.currentThread().getName();
    }
    
    public static void main(String args[]){
        //Get ExecutorService from Executors utility class, thread pool size is 10
        ExecutorService executor = Executors.newFixedThreadPool(10);
        //create a list to hold the Future object associated with Callable
        List<Future<String>> list = new ArrayList<Future<String>>();
        //Create MyCallable instance
        Callable<String> callable = new MyCallable();
        for(int i=0; i< 100; i++){
            //submit Callable tasks to be executed by thread pool
            Future<String> future = executor.submit(callable);
            //add Future to the list, we can get return value using Future
            list.add(future);
        }
        for(Future<String> fut : list){
            try {
                //print the return value of Future, notice the output delay in console
                // because Future.get() waits for task to get completed
                System.out.println(new Date()+ "::"+fut.get());
            } catch (InterruptedException | ExecutionException e) {
                e.printStackTrace();
            }
        }
        //shut down the executor service now
        executor.shutdown();
    }

}

Popularity 9/10 Helpfulness 2/10 Language java

Source: Grepper

Tags: java

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Contributed on Feb 22 2023

Pragya Keshap

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