www.pudn.com > ThinkinginJava4thEdition(SourceCode).zip > ActiveObjectDemo.java

//: concurrency/ActiveObjectDemo.java 
// Can only pass constants, immutables, "disconnected 
// objects," or other active objects as arguments 
// to asynch methods. 
import java.util.concurrent.*; 
import java.util.*; 
import static net.mindview.util.Print.*; 
 
public class ActiveObjectDemo { 
  private ExecutorService ex = 
    Executors.newSingleThreadExecutor(); 
  private Random rand = new Random(47); 
  // Insert a random delay to produce the effect 
  // of a calculation time: 
  private void pause(int factor) { 
    try { 
      TimeUnit.MILLISECONDS.sleep( 
        100 + rand.nextInt(factor)); 
    } catch(InterruptedException e) { 
      print("sleep() interrupted"); 
    } 
  } 
  public Future 
  calculateInt(final int x, final int y) { 
    return ex.submit(new Callable() { 
      public Integer call() { 
        print("starting " + x + " + " + y); 
        pause(500); 
        return x + y; 
      } 
    }); 
  } 
  public Future 
  calculateFloat(final float x, final float y) { 
    return ex.submit(new Callable() { 
      public Float call() { 
        print("starting " + x + " + " + y); 
        pause(2000); 
        return x + y; 
      } 
    }); 
  } 
  public void shutdown() { ex.shutdown(); } 
  public static void main(String[] args) { 
    ActiveObjectDemo d1 = new ActiveObjectDemo(); 
    // Prevents ConcurrentModificationException: 
    List> results = 
      new CopyOnWriteArrayList>(); 
    for(float f = 0.0f; f < 1.0f; f += 0.2f) 
      results.add(d1.calculateFloat(f, f)); 
    for(int i = 0; i < 5; i++) 
      results.add(d1.calculateInt(i, i)); 
    print("All asynch calls made"); 
    while(results.size() > 0) { 
      for(Future f : results) 
        if(f.isDone()) { 
          try { 
            print(f.get()); 
          } catch(Exception e) { 
            throw new RuntimeException(e); 
          } 
          results.remove(f); 
        } 
    } 
    d1.shutdown(); 
  } 
} /* Output: (85% match) 
All asynch calls made 
starting 0.0 + 0.0 
starting 0.2 + 0.2 
0.0 
starting 0.4 + 0.4 
0.4 
starting 0.6 + 0.6 
0.8 
starting 0.8 + 0.8 
1.2 
starting 0 + 0 
1.6 
starting 1 + 1 
0 
starting 2 + 2 
2 
starting 3 + 3 
4 
starting 4 + 4 
6 
8 
*///:~