// concurrency/CallableDemo.java
// (c)2016 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
import java.util.concurrent.*;
import java.util.*;

class TaskWithResult implements Callable<String> {
  private int id;
  public TaskWithResult(int id) {
    this.id = id;
  }
  @Override
  public String call() {
    return "result of TaskWithResult " + id;
  }
}

public class CallableDemo {
  public static void main(String[] args) {
    ExecutorService exec = Executors.newCachedThreadPool();
    ArrayList<Future<String>> results = new ArrayList<>();
    for(int i = 0; i < 10; i++)
      results.add(exec.submit(new TaskWithResult(i)));
    for(Future<String> fs : results)
      try {
        // get() blocks until completion:
        System.out.println(fs.get());
      } catch(InterruptedException e) {
        System.out.println(e);
        return;
      } catch(ExecutionException e) {
        System.out.println(e);
      } finally {
        exec.shutdown();
      }
  }
}
/* Output:
result of TaskWithResult 0
result of TaskWithResult 1
result of TaskWithResult 2
result of TaskWithResult 3
result of TaskWithResult 4
result of TaskWithResult 5
result of TaskWithResult 6
result of TaskWithResult 7
result of TaskWithResult 8
result of TaskWithResult 9
*/