doublebinding.java

一个关于java 的常用工具包

package org.jutil.structure;
/**
 * <p><b>DEPRECATED</b>A class of "components" for implementing a double binding.</p>
 *
 * <p>This is actually a lightweight version of the APSet-APElement combination
 * of the <a href="http://www.beedra.org">Beedra</a> framework of Jan Dockx.</p>
 * 
 * <p>The classes that are linked together should still be in the same package,
 * but are easier to implement using DoubleBinding. A "native" binding is more
 * efficient, but an optimizer could do the transformation in order to get both
 * the programming and the efficiency benefits.</p>
 *
 * <p>This class is typically used in the following way:</p>
 *
 *<pre><code>
 * public class A {
 *   public A() {
 *     $b= new DoubleBinding(this);
 *   }
 * 
 *   public B getB() {
 *     return (B)$b.getOtherEnd();
 *   }
 * 
 *   public void setB(B b) {
 *     if (b != null) {
 *       $b.setOtherBinding(b.getALink());
 *     }
 *     else {
 *       $b.setOtherBinding(null);
 *     }
 *   }
 * 
 *   private DoubleBinding $b;
 *   private String $name;
 * }
 * 
 * public class B {
 * 
 *   public B() {
 *     $a = new DoubleBinding(this);
 *   }
 * 
 *   public A getA() {
 *     return (A)$a.getOtherEnd();
 *   }
 * 
 *   DoubleBinding getALink() {
 *     return $a;
 *   }
 *   private String $name;
 * }
 *</code></pre>
 * @path    $Source: /cvsroot/org-jutil/jutil.org/src/org/jutil/structure/DoubleBinding.java,v $
 * @version $Revision: 1.7 $
 * @date    $Date: 2002/07/21 10:30:35 $
 * @state   $State: Exp $
 * @author  Marko van Dooren
 * @release $Name:  $
 *
 * @deprecated
 */
public class DoubleBinding {

 	/* The revision of this class */
	public final static String CVS_REVISION ="$Revision: 1.7 $";

/*@
	 @ public invariant getObject() != null;
   @ public invariant getOtherBinding() != null ==>
   @                  getOtherBinding().getOtherBinding() == this;
   @*/

  /**
   * Initialize a new unconnected DoubleBinding.
   *
   * @param object
   *        The object on this side of the double binding
   */
 /*@
   @ public behavior
   @
   @ pre object != null;
   @
   @ post getOtherBinding() == null;
   @ post getObject() == object;
   @*/
  public DoubleBinding(Object object) {
    _object=object;
  }

  /**
   * Initialize a new double binding connected to the given
   * other DoubleBinding.
   *
   * @param other
   *        The DoubleBinding object to connect to.
   * @param object
   *        The object on this side of the double binding
   */
 /*@
   @ public behavior
   @
   @ pre object != null;
   @
   @ post getOtherBinding() == otherBinding;
   @ post otherBinding != null ==> otherBinding.getOtherBinding() == this;
   @ // If <other> was connected before to another object, that other object will
   @ // be disconnected.
   @ post (otherBinding != null) && \old(otherBinding.getOtherBinding()) != null ==>
   @      \old(otherBinding.getOtherBinding()).getOtherBinding() == null;
   @ post getObject() == object;
   @*/
  public DoubleBinding(DoubleBinding otherBinding, Object object) {
    _object=object;
    setOtherBinding(otherBinding);
  }

  /**
   * Return the object at this side of the double binding.
   */
  public Object getObject() {
    return _object;
  }
	
	/**
	 * Check whether or not this DoubleBinding is connected to another.
	 */
	public boolean isConnected() {
		return (_otherBinding != null);
  }

  /**
   * Return the Object at the other end of this double binding.
   */
 /*@
   @ public behavior
   @
   @ post getOtherBinding() == null ==> \result == null;
   @ post getOtherBinding() != null ==> \result == getOtherBinding().getObject();
   @*/
  public Object getOtherEnd() {
    if (getOtherBinding() == null) {
        return null;
    }
    return getOtherBinding().getObject();
  }

  /**
   * Return the DoubleBinding object this one is connected to.
   */
  public DoubleBinding getOtherBinding() {
    return _otherBinding;
  }

  /**
   * Set the other end of this binding
   *
   * @param otherBinding
   *        The new DoubleBinding object that will be connected to this.
   */
 /*@
   @ public behavior
   @
   @ post getOtherBinding() == otherBinding;
   @ // If this DoubleBinding was connected before, and will now be
   @ // connected to another DoubleBinding, the DoubleBinding it was
   @ // connected to will be disconnected.
   @ post \old(getOtherBinding()) != null && \old(getOtherBinding()) != otherBinding ==>
   @      \old(getOtherBinding()).getOtherBinding() == null;
   @ post otherBinding != null ==> otherBinding.getOtherBinding() == this;
   @ // If <other> was connected before to another object, that other object will
   @ // be disconnected.
   @ post otherBinding != null &&
	 @      \old(otherBinding.getOtherBinding()) != null &&
   @      \old(otherBinding.getOtherBinding()) != this ==>
   @      \old(otherBinding.getOtherBinding()).getOtherBinding() == null;
   @*/
  public void setOtherBinding(DoubleBinding otherBinding) {
		// only do something if we have to.
		if(otherBinding != _otherBinding) {
			if(_otherBinding != null) {
				_otherBinding.disconnect();
			}
			// do this first, or we will end up in an infinite loop
      // or we need to introduce yet another method.
			_otherBinding=otherBinding;
      // If this is the DoubleBinding on which the change was initiated, we
      // need to tell the new other side to connect to us. Otherwise, that
      // binding is already set up, and we do nothing.
      if((otherBinding != null) && (otherBinding.getOtherBinding() != this)){
          otherBinding.setOtherBinding(this);
      }
    }
  }

  /**
   * Disconnect this DoubleBinding on one side/
   */
 /*@
   @ public behavior
   @
   @ post ! isConnected();
   @*/
  private void disconnect() {
    _otherBinding = null;
  }

  /**
   * the DoubleBinding object this one is connected to.
   * May be null.
   */
  private DoubleBinding _otherBinding;

  /**
   * The object at this side of the double binding.
   */
 /*@
   @ private invariant _object != null;
   @*/
  private Object _object;
}
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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
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or FITNESS FOR A PARTICULAR PURPOSE. See the JUTIL.ORG Software 
License for more details.
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