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    1   /*
    2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/NotFunction.java,v 1.8 2005/06/28 13:44:45 elharo Exp $
    3    * $Revision: 1.8 $
    4    * $Date: 2005/06/28 13:44:45 $
    5    *
    6    * ====================================================================
    7    *
    8    * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
    9    * All rights reserved.
    10   *
    11   * Redistribution and use in source and binary forms, with or without
    12   * modification, are permitted provided that the following conditions
    13   * are met:
    14   *
    15   * 1. Redistributions of source code must retain the above copyright
    16   *    notice, this list of conditions, and the following disclaimer.
    17   *
    18   * 2. Redistributions in binary form must reproduce the above copyright
    19   *    notice, this list of conditions, and the disclaimer that follows
    20   *    these conditions in the documentation and/or other materials
    21   *    provided with the distribution.
    22   *
    23   * 3. The name "Jaxen" must not be used to endorse or promote products
    24   *    derived from this software without prior written permission.  For
    25   *    written permission, please contact license@jaxen.org.
    26   *
    27   * 4. Products derived from this software may not be called "Jaxen", nor
    28   *    may "Jaxen" appear in their name, without prior written permission
    29   *    from the Jaxen Project Management (pm@jaxen.org).
    30   *
    31   * In addition, we request (but do not require) that you include in the
    32   * end-user documentation provided with the redistribution and/or in the
    33   * software itself an acknowledgement equivalent to the following:
    34   *     "This product includes software developed by the
    35   *      Jaxen Project <http://www.jaxen.org/>."
    36   * Alternatively, the acknowledgment may be graphical using the logos
    37   * available at http://www.jaxen.org/
    38   *
    39   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
    40   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    41   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    42   * DISCLAIMED.  IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
    43   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    44   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    45   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
    46   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    47   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    48   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
    49   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    50   * SUCH DAMAGE.
    51   *
    52   * ====================================================================
    53   * This software consists of voluntary contributions made by many
    54   * individuals on behalf of the Jaxen Project and was originally
    55   * created by bob mcwhirter <bob@werken.com> and
    56   * James Strachan <jstrachan@apache.org>.  For more information on the
    57   * Jaxen Project, please see <http://www.jaxen.org/>.
    58   *
    59   * $Id: NotFunction.java,v 1.8 2005/06/28 13:44:45 elharo Exp $
    60   */
    61
    62  package org.jaxen.function;
    63
    64  import java.util.List;
    65
    66  import org.jaxen.Context;
    67  import org.jaxen.Function;
    68  import org.jaxen.FunctionCallException;
    69  import org.jaxen.Navigator;
    70
    71  /***
    72   * <p><b>4.3</b> <code><i>boolean</i> not(<i>boolean</i>)</code> </p>
    73   *
    74   *
    75   * <blockquote src="http://www.w3.org/TR/xpath#function-not">
    76   * The <b>not</b> function returns true if its argument is false, and false otherwise.
    77   * </blockquote>
    78   *
    79   * @author bob mcwhirter (bob @ werken.com)
    80   * @see <a href="http://www.w3.org/TR/xpath#function-not" target="_top">Section 4.3 of the XPath Specification</a>
    81   */
    82  public class NotFunction implements Function
    83  {
    84
    85      /***
    86       * Create a new <code>NotFunction</code> object.
    87       */
    88      public NotFunction() {}
    89
    90      /***
    91       * Returns <code>Boolean.TRUE</code> if the boolean value of
    92       * <code>args.get(0)</code> is false, and <code>Boolean.FALSE</code> otherwise.
    93       * The boolean value is calculated as if by the XPath <code>boolean</code>
    94       * function.
    95       *
    96       * @param context the context at the point in the
    97       *         expression where the function is called
    98       * @param args a single element list
    99       *
    100      * @return <code>Boolean.TRUE</code> if the boolean value of
    101      * <code>obj</code> is false, and <code>Boolean.FALSE</code> otherwise
    102      *
    103      * @throws FunctionCallException if <code>args</code> does not have exactly one argument
    104      */
    105     public Object call(Context context,
    106                        List args) throws FunctionCallException
    107     {
    108         if (args.size() == 1)
    109         {
    110             return evaluate( args.get(0), context.getNavigator() );
    111         }
    112
    113         throw new FunctionCallException( "not() requires one argument." );
    114     }
    115
    116     /***
    117      * Returns <code>Boolean.TRUE</code> if the boolean value of
    118      * <code>obj</code> is false, and <code>Boolean.FALSE</code> otherwise.
    119      * The boolean value is calculated as if by the XPath <code>boolean</code>
    120      * function.
    121      *
    122      * @param obj the object whose boolean value is inverted
    123      * @param nav the <code>Navigator</code> used to calculate the boolean value of <code>obj</code>
    124      *
    125      * @return <code>Boolean.TRUE</code> if the boolean value of
    126      * <code>obj</code> is false, and <code>Boolean.FALSE</code> otherwise
    127      */
    128     public static Boolean evaluate(Object obj, Navigator nav)
    129     {
    130         return ( ( BooleanFunction.evaluate( obj, nav ).booleanValue() )
    131                  ? Boolean.FALSE
    132                  : Boolean.TRUE
    133                  );
    134     }
    135
    136 }