How to use invokeAll() to let all thread pool do their task?

Question

    ExecutorService pool=Executors.newFixedThreadPool(7);
        List> future=new ArrayList>();
        List<         


        

Answer 1

Future.get() throws below exceptions.

CancellationException - if the computation was cancelled

ExecutionException - if the computation threw an exception

InterruptedException - if the current thread was interrupted while waiting

Catch all these exceptions when you call get() method.

I have simulated divide by zero exception for some Callable tasks but exception in one Callable does not affect other Callable tasks submitted to ExecutorService if you catch above three exceptions as shown in example code.

Example code snippet:

import java.util.concurrent.*;
import java.util.*;

public class InvokeAllUsage{
    public InvokeAllUsage(){
        System.out.println("creating service");
        ExecutorService service = Executors.newFixedThreadPool(10);

        List futureList = new ArrayList();
        for ( int i=0; i<10; i++){
            MyCallable myCallable = new MyCallable((long)i+1);
            futureList.add(myCallable);
        }
        System.out.println("Start");
        try{
            List> futures = service.invokeAll(futureList);  
            for(Future future : futures){
                try{
                    System.out.println("future.isDone = " + future.isDone());
                    System.out.println("future: call ="+future.get());
                }
                catch (CancellationException ce) {
                    ce.printStackTrace();
                } catch (ExecutionException ee) {
                    ee.printStackTrace();
                } catch (InterruptedException ie) {
                    Thread.currentThread().interrupt(); // ignore/reset
                }
            }
        }catch(Exception err){
            err.printStackTrace();
        }
        System.out.println("Completed");
        service.shutdown();
    }
    public static void main(String args[]){
        InvokeAllUsage demo = new InvokeAllUsage();
    }
    class MyCallable implements Callable{
        Long id = 0L;
        public MyCallable(Long val){
            this.id = val;
        }
        public Long call(){

            if ( id % 5 == 0){
                id = id / 0;
            }           
            return id;
        }
    }
}

output:

creating service
Start
future.isDone = true
future: call =1
future.isDone = true
future: call =2
future.isDone = true
future: call =3
future.isDone = true
future: call =4
future.isDone = true
java.util.concurrent.ExecutionException: java.lang.ArithmeticException: / by zero
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:188)
        at InvokeAllUsage.(InvokeAllUsage.java:20)
        at InvokeAllUsage.main(InvokeAllUsage.java:37)
Caused by: java.lang.ArithmeticException: / by zero
        at InvokeAllUsage$MyCallable.call(InvokeAllUsage.java:47)
        at InvokeAllUsage$MyCallable.call(InvokeAllUsage.java:39)
        at java.util.concurrent.FutureTask.run(FutureTask.java:262)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:744)
future.isDone = true
future: call =6
future.isDone = true
future: call =7
future.isDone = true
future: call =8
future.isDone = true
future: call =9
future.isDone = true
java.util.concurrent.ExecutionException: java.lang.ArithmeticException: / by zero
        at java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.util.concurrent.FutureTask.get(FutureTask.java:188)
        at InvokeAllUsage.(InvokeAllUsage.java:20)
        at InvokeAllUsage.main(InvokeAllUsage.java:37)
Caused by: java.lang.ArithmeticException: / by zero
        at InvokeAllUsage$MyCallable.call(InvokeAllUsage.java:47)
        at InvokeAllUsage$MyCallable.call(InvokeAllUsage.java:39)
        at java.util.concurrent.FutureTask.run(FutureTask.java:262)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:744)
Completed