Threads - Beginning Java 8 Language Features - page 269

throw e;
}
}
return new TaskResult(taskId, totalSleepTime);
}
}
Listing 6-57. A Class to Test the Completion Service
// CompletionServiceTest.java
package com.jdojo.threads;
import java.util.concurrent.Future;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorCompletionService;
public class CompletionServiceTest {
public static void main(String[] args) {
// Get an executor with three threads in its thread pool
ExecutorService exec = Executors.newFixedThreadPool(3);
// Completed task returns an object of the TaskResult class
ExecutorCompletionService<TaskResult> completionService =
new ExecutorCompletionService<>(exec);
// Submit five tasks and each task will sleep three times for a random period
// between 1 and 10 seconds
for(int i = 1; i <= 5; i++) {
SleepingTask task = new SleepingTask(i, 3);
completionService.submit(task);
}
// Print the result of each task as they are completed
for(int i = 1; i <= 5; i++) {
try {
Future<TaskResult> completedTask =
completionService.take();
TaskResult result= completedTask.get();
System.out.println("Completed a task - " + result);
}
catch (ExecutionException ex) {
System.out.println("Error in executing the task.");
}
catch (InterruptedException ex) {
System.out.println("Task execution has been interrupted.");
}
}