NegotiableCollection.java :  » 6.0-JDK-Modules » Java-Advanced-Imaging » javax » media » jai » remote » Java Open Source

/*
 * $RCSfile: NegotiableCollection.java,v $
 *
 * Copyright (c) 2005 Sun Microsystems, Inc. All rights reserved.
 *
 * Use is subject to license terms.
 *
 * $Revision: 1.1 $
 * $Date: 2005/02/11 04:57:51 $
 * $State: Exp $
 */package javax.media.jai.remote;

import java.util.Collection;
import java.util.Iterator;
import java.util.Vector;

/**
 * A class that wraps an <code>Collection</code> to implement the 
 * <code>Negotiable</code> interface. <code>NegotiableCollection</code>
 * is a convenience class to specify a <code>Negotiable</code> value for
 * a parameter whose valid values are contained in an <code>Collection</code>.
 *
 * @since JAI 1.1
 */
public class NegotiableCollection implements Negotiable {

    private Vector elements;
    private Class elementClass;
    
    /**
     * Creates a <code>NegotiableCollection</code> given an
     * <code>Collection</code>.
     *
     * @throws IllegalArgumentException if collection is null.
     * @throws IllegalArgumentException if all the elements of collection 
     * are not of the same <code>Class</code> type.
     */
    public NegotiableCollection(Collection collection) {

  if (collection == null) {
      throw new IllegalArgumentException(
         JaiI18N.getString("NegotiableCollection0"));
  }

  elements = new Vector();
  Object obj;

  Iterator i = collection.iterator();
  if (i.hasNext()) {
      obj = i.next();
      elements.add(obj);
      elementClass = obj.getClass();
  } else {
      // no elements, so elementClass will be initialized to null,
      // which is correct. elements will also be null, which is 
      // also correct.
  }

  for ( ;i.hasNext(); ) {
      obj = i.next();
      if (obj.getClass() != elementClass) {
    throw new IllegalArgumentException(
         JaiI18N.getString("NegotiableCollection1"));
      }
      elements.add(obj);
  }
    }

    /**
     * Creates a <code>NegotiableCollection</code> given an array of 
     * <code>Object</code>s. The elements of the <code>Object</code>
     * array are treated as being the elements of an <code>Collection</code>.
     *
     * @throws IllegalArgumentException if objects is null.
     * @throws IllegalArgumentException if all the elements of objects are not
     * of the same <code>Class</code> type.
     */
    public NegotiableCollection(Object objects[]) {

  if (objects == null) {
      throw new IllegalArgumentException(
         JaiI18N.getString("NegotiableCollection0"));
  }

  int length = objects.length;
  if (length != 0) {
      elementClass = objects[0].getClass();
  } else {
      // no elements, so elementClass will be initialized to null,
      // which is correct. elements will also be null, which is 
      // also correct.
  }

  elements = new Vector(length);
  for (int i=0; i<length; i++) {
      if (objects[i].getClass() != elementClass) {
    throw new IllegalArgumentException(
         JaiI18N.getString("NegotiableCollection1"));
      }
      elements.add(objects[i]);
  }
    }

    /**
     * Returns the <code>Collection</code> of values which are currently
     * valid for this class, null if there are no valid values.
     */
    public Collection getCollection() {
  if (elements.isEmpty())
      return null;
  return elements;
    }

    /**
     * Returns a <code>NegotiableCollection</code> that contains those
     * elements that are common to this <code>NegotiableCollection</code>
     * and the one supplied. If the supplied <code>Negotiable</code> is not
     * a <code>NegotiableCollection</code> with its elements being of the 
     * same <code>Class</code> as this class', or if there are no common
     * elements, the negotiation will fail and <code>null</code> (signifying
     * the failure of the negotiation) will be returned.
     *
     * @param other The <code>Negotiable</code> to negotiate with.
     */
    public Negotiable negotiate(Negotiable other) {

  if (other == null) {
      return null;
  }

  // if other is not an instance of NegotiableCollection
  if (!(other instanceof NegotiableCollection) || 
      other.getNegotiatedValueClass() != elementClass) {
      return null;
  }
  
  Object obj;
  Vector result = new Vector();

  Collection otherCollection =
      ((NegotiableCollection)other).getCollection();

  // If the collection is null, i.e there are no valid values, then 
  // negotiation fails.
  if (otherCollection == null) 
      return null;
  
  // Return a NegotiableCollection whose elements are those that
  // were common to both the collections.
  for (Iterator i=elements.iterator(); i.hasNext(); ) {
      obj = i.next();
      // If element is present in both the collections
      if (otherCollection.contains(obj)) {
    // Do not insert duplicates
    if (!result.contains(obj)) {
        result.add(obj);
    }
      }
  }

  // If there are no common elements, negotiation failed.
  if (result.isEmpty()) {
      return null;
  }

  return new NegotiableCollection(result);
    }

    /**
     * Returns a single value that is valid for this 
     * <code>NegotiableCollection</code>. The returned value is the first
     * element contained in this <code>NegotiableCollection</code>. Returns
     * <code>null</code> if there are no valid elements in this
     * <code>NegotiableCollection</code>.
     */
    public Object getNegotiatedValue() {
  
  // Return the first element in this NegotiableCollection
  // else return 
  // <code>null</code> 
  if (elements != null && elements.size() > 0) {
      return elements.elementAt(0);
  } else {
      return null;
  }
    }

    /**
     * Returns the <code>Class</code> of the Object returned as the result
     * of the negotiation. If the <code>Collection</code> used to construct
     * this <code>NegotiableCollection</code> was empty, i.e. had no
     * elements, the <code>Class</code> of the elements is indeterminate, 
     * therefore null will be returned from this method in such a case.
     */
    public Class getNegotiatedValueClass() {
  return elementClass;
    }
}