Listing 1: A Cougaar Plug-In
 // Cougaar classes are in the 'alp' packages
import alp.cluster.IncrementalSubscription;
import alp.util.UnaryPredicate;
import java.util.Enumeration;

public class ExamplePlugIn extends alp.plugin.SimplePlugIn
{
  private IncrementalSubscription
          allStringsSubscription;
  private UnaryPredicate allStringsPredicate =
          new UnaryPredicate() {
    public boolean execute(Object o) {
      return o instanceof String;
    }};

  /**
   * Establish subscription for Strings
   **/
  public void setupSubscriptions() {
    allStringsSubscription =
    (IncrementalSubscription)subscribe(
         allStringsPredicate);
  }

  /**
 
 

 * Handle changes to the subscription
   **/
  public void execute() {
 
 

 Enumeration e =
      allStringsSubscription.elements();
    while(e.hasMoreElements())
    {
      System.out.println("Got a string: "+
      e.nextElement());
    }
  }
}