package org.jutil.relation;import java.util.List;/** * <p>A class of objects that can be used to set up bi-directional relations between objects.</p> * * <center><img src="doc-files/Relation.png"/></center> * * <p>This class provides the general interface that is needed in order to create different types  * of bindings that can be created by taking two arbitrary multiplicities.</p> * * @path    $Source: /cvsroot/org-jutil/jutil.org/src/org/jutil/relation/Relation.java,v $ * @version $Revision: 1.8 $ * @date    $Date: 2002/09/03 13:12:34 $ * @state   $State: Exp $ * @author  Marko van Dooren * @release $Name:  $ */public abstract class Relation {    /**   * Initialize a new Relation for the given object.   * The new Relation will be unconnected.   *   * @param object   *        The object at this side of the binding.   */ /*@   @ public behavior   @   @ pre object != null;   @   @ post getObject() == object;   @*/  public Relation(Object object) {    _object = object;  }  /**   * Check whether or not the given Relation is connected   * to this one.   *   * @param relation   *        The relation which is possibly on the other end   *        of the binding.   */ /*@   @ public behavior   @   @ post \result == getOtherRelations().contains(relation);   @*/  public boolean contains(Relation relation) {    return getOtherRelations().contains(relation);  } /*@   @ also public behavior   @   @ post \result == (other == this);   @*/  public boolean equals(Object other) {    return other == this;  }  /**   * Add the given Relation as a participant in this   * binding.   */ /*@   @ protected behavior   @   @ pre isValidElement(other);   @   @ post registered(\old(getOtherRelations()), other);   @*/  protected abstract void register(Relation other);  /**   * Remove the given Relation as a participant in this   * binding.   */ /*@   @ protected behavior   @   @ pre contains(other);   @   @ post unregistered(\old(getOtherRelations()), other);   @*/  protected abstract void unregister(Relation other);  /**   * Check whether or not the given Relation may be connected to   * this Relation.   */ /*@   @ public behavior   @   @ post \result == true | \result == false;   @*/  protected abstract boolean isValidElement(Relation relation);  /**   * Check whether or not the current state corresponds to connecting   * to the given Relation when being connected to the Relations   * in the given list.   *   * @param oldConnections   *        The List of Relations this Relation was connected to before.   * @param registered   *        The Relation this Relation has connected to.   */ /*@   @ public behavior   @   @ pre oldConnections != null;   @ pre ! oldConnections.contains(null);   @ pre (\forall Object o; oldConnections.contains(o); o instanceof Relation);   @   @ post ! contains(registered) ==> \result == false;   @ post ! (\forall Relation r; r != registered;   @          oldConnections.contains(r) == contains(r)) ==> \result == false;   @*/  public abstract boolean registered(List oldConnections, Relation registered);  /**   * Check whether or not the current state corresponds to disconnecting   * from the given Relation when being connected to the Relations   * in the given list.   *   * @param oldConnections   *        The List of Relations this Relation was connected to before.   * @param registered   *        The Relation this Relation has connected to.   */ /*@   @ public behavior   @   @ pre oldConnections != null;   @ pre ! oldConnections.contains(null);   @ pre (\forall Object o; oldConnections.contains(o); o instanceof Relation);   @   @ post contains(unregistered) ==> \result == false;   @ post ! oldConnections.contains(unregistered) ==> \result == false;   @ post ! (\forall Relation r; r != unregistered;   @          oldConnections.contains(r) == contains(r)) ==> \result == false;   @*/  public abstract boolean unregistered(List oldConnections, Relation unregistered);  /**   * Return the objects on the other side of the binding.   */ /*@   @ public behavior   @   @ post \result != null;   @ post \result.size() == getOtherRelations().size();   @ post (\forall Object o; \result.contains(o);   @        (\exists Relation r; getOtherRelations().contains(r);   @           r.getObject() == o));   @*/  public abstract List getOtherEnds();  /**   * Return the Relations on the other side of the binding.   */ /*@   @ public behavior   @   @ post \result != null;   @ post (\forall Object o; \result.contains(o); o instanceof Relation);   @ post ! \result.contains(null);   @*/  public abstract List getOtherRelations();  /**   * Return the object on the n side of the 1-n binding represented by   * this OneSide   */ /*@   @ public behavior   @   @ post \result != null;   @*/  public Object getObject() {    return _object;   }    /**   * The object on this side of the binding.   */  private Object _object;}/* * <copyright>Copyright (C) 1997-2001. This software is copyrighted by  * the people and entities mentioned after the "@author" tags above, on  * behalf of the JUTIL.ORG Project. The copyright is dated by the dates  * after the "@date" tags above. All rights reserved. * This software is published under the terms of the JUTIL.ORG Software * License version 1.1 or later, a copy of which has been included with * this distribution in the LICENSE file, which can also be found at * http://org-jutil.sourceforge.net/LICENSE. This software is distributed  * WITHOUT ANY WARRANTY; without even the implied warranty of  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  * See the JUTIL.ORG Software License for more details. For more information, * please see http://org-jutil.sourceforge.net/</copyright> */