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

public class ExecutorTest5_1 {
    public ExecutorTest5_1() {
        ExecutorService e = Executors.newSingleThreadExecutor();
        
        List<Callable<String>> tasks = new ArrayList<Callable<String>>();
        for (int i = 0; i < 5; i++) {
            Callable<String> task = new CallableTask("task" + i);
            tasks.add(task);
        }

        try {
            String result = e.invokeAny(tasks);
            System.out.println("Result: " + result);
        } catch (ExecutionException ex) {
            ex.printStackTrace();
        } catch (InterruptedException ex) {
            ex.printStackTrace();
        }

        e.shutdown();
    }

    class CallableTask implements Callable<String> {
        private String name;

        public CallableTask(String name) {
            this.name = name;
        }

        public String call() {
            System.out.println(name + " is Called.");
            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException ex) {}

            System.out.println(name + " exits.");
            return name;
        }
    }

    public static void main(String[] args) {
        new ExecutorTest5_1();
    }
}