forall.java

一个关于java 的常用工具包

package org.jutil.java.collections;


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

/**
 * <p>A boolean for-all operator.</p>
 *
 * <center>
 *   <img src="doc-files/ForAll.png"/>
 * </center>
 *
 * <p>A convenience accumulator of collections that checks whether all
 * elements of a collection satisfy the criterion defined in the abstract 
 * method <code>public boolean criterion(Object element)</code>.</p>
 *
 * <p>As with <code>Accumulator</code>, this class can best be used as an anonymous
 * inner class.</p>
 *<pre><code>
 *boolean bool =
 *  new ForAll() {
 *
 *       /oo
 *         o also public behavior
 *         o
 *         o post (* additional precondition for criterion method *)
 *         o
 *         o public model boolean isValidElement(Object element);
 *         o/
 *
 *       /oo
 *         o also public behavior
 *         o
 *         o post \result == ((MyType)element.someProperty() ...)
 *         o/
 *        public boolean criterion(Object element) {
 *          // criterion code
 *        }
 *      }.in(collection);
 *</code></pre>
 * 
 * @path    $Source: /cvsroot/org-jutil/jutil.org/src/org/jutil/java/collections/ForAll.java,v $
 * @version $Revision: 1.19 $
 * @date    $Date: 2002/07/20 19:11:30 $
 * @state   $State: Exp $
 * @author  Marko van Dooren
 * @author  Jan Dockx
 * @release $Name:  $
 */
public abstract class ForAll extends BooleanAccumulator {

  public final static String CVS_REVISION="$Revision: 1.19 $";
	
  /**
   * Check whether the given object satisfies the criterion
   * for this ForAll accumulator.
   */
 /*@
   @ public behavior
   @
   @ pre isValidElement(element);
   @
   @ // criterion should be consistent with equals; subclass can say more
   @ post (\forall Object o1;;
   @        (\forall Object o2; o2.equals(o1); criterion(o1) == criterion(o2)));
   @*/
  public abstract boolean criterion(Object element);
  
 /*@
   @ also public behavior
   @
   @ post \result == true;
   @*/
  final public boolean initialAccumulator() {
    return true;
  }
  
  /*@
    @ also public behavior
    @
    @ post \result == (acc && criterion(element));
    @*/
  final public boolean accumulate(Object element, boolean acc) {
    return (criterion(element) && acc);
  }
  
 /*@
   @ also public behavior
   @
   @ post \result == (\forall Object o; collection.contains(o); criterion(o));
   @*/
  public boolean in(Collection collection) {
    boolean acc = true;
		if(collection != null) {
    	Iterator iter = collection.iterator();
    	// variant : the number of elements in the explicit collection that
    	//           have not yet been checked.
    	// invariant : acc == true if all previous elements in the explicit collection
    	//             satisfy the criterion. Otherwise, it is false.
    	while (iter.hasNext() && acc) {
      	acc = accumulate(iter.next(), acc);
    	}
    }
    return acc;
  }
	

}

/*<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>*/