negationasfailure.java

一个关于java 的常用工具包

package org.jutil.predicate;

import java.util.List;
import java.util.ArrayList;
/*@ model import org.jutil.java.collections.Collections; @*/

/**
 * <p>A class of predicates that wrap another predicate and treat the 
 * occurrence of an exception in
 * <a href="NegationAsFailure.html#eval(java.lang.Object)"><code>eval()</code></a>
 * as <code>false</code>.</p>
 *
 * <center><img src="doc-files/NegationAsFailure.png"/></center>
 *
 * <p>Note that if you wrap a NegationAsFailure object in another predicate,
 * you will not get the same result as when switching the wrapping predicate
 * and the NegationAsFailure. E.g. <code>new Not(new NegationAsFailure(predicate))</code>
 * will not always return the same value as <code>new NegationAsFailure(new Not(predicate))</code>.</p>
 *
 * @path    $Source: /cvsroot/org-jutil/jutil.org/src/org/jutil/predicate/NegationAsFailure.java,v $
 * @version $Revision: 1.3 $
 * @date    $Date: 2002/07/21 16:06:38 $
 * @state   $State: Exp $
 * @author  Marko van Dooren
 * @release $Name:  $
 */
public class NegationAsFailure extends TotalPredicate {
	
  /* The revision of this class */
    public final static String CVS_REVISION ="$Revision: 1.3 $";
    
    /**
	 * Initialize a new NegationAsFailure with the given predicate.
	 *
	 * @param predicate
	 *        The predicate to be wrapped.
	 */
 /*@
	 @ public behavior
	 @
	 @ pre predicate != null;
	 @
	 @ post getPredicate() == predicate;
	 @*/
	public NegationAsFailure(Predicate predicate) {
		$predicate = predicate;
	}

  /*@
	  @ also public behavior
		@
		@ post getPredicate().isValidElement(object) ==> \result == getPredicate().eval(object);
		@ post ! getPredicate().isValidElement(object) ==> false;
		@*/
	public boolean eval(Object object) {
		//MVDMVDMVD: the spec is not correct, FIX IT
		try {
			return $predicate.eval(object);
		}
		catch(Exception exc) {
			return false;
		}
	}

	/**
	 * Return the wrapped predicate.
	 */
 /*@
   @ public behavior
 	 @
	 @ post \result == getSubPredicates().get(1);
	 @*/
	public Predicate getPredicate() {
		return $predicate;
	}

 /*@
	 @ also public behavior
	 @
	 @ post Collections.containsExplicitly(\result, getPredicate());
	 @ post \result.size() == 1;
	 @*/
	public List getSubPredicates() {
		List result = new ArrayList();
		result.add($predicate);
		return result;
	}

  /**
	 * See superclass
	 */
	public int nbSubPredicates() {
		return 1;
	}

  /**
   * The wrapped predicate.
   */
 /*@
	 @ private invariant $predicate != null;
	 @ private invariant $predicate != this;
	 @*/
	private Predicate $predicate;
}
/*
 * <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>
 */