1. /*

  2.  * Copyright  2001-2002,2004 The Apache Software Foundation

  3.  *

  4.  *  Licensed under the Apache License, Version 2.0 (the "License");

  5.  *  you may not use this file except in compliance with the License.

  6.  *  You may obtain a copy of the License at

  7.  *

  8.  *      http://www.apache.org/licenses/LICENSE-2.0

  9.  *

  10.  *  Unless required by applicable law or agreed to in writing, software

  11.  *  distributed under the License is distributed on an "AS IS" BASIS,

  12.  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  13.  *  See the License for the specific language governing permissions and

  14.  *  limitations under the License.

  15.  *

  16.  */

  17. 

  18. package org.apache.tools.ant.taskdefs.condition;

  19. 

  20. import org.apache.tools.ant.BuildException;

  21. 

  22. /**

  23.  * <not> condition.

  24.  *

  25.  * Evaluates to true if the single condition nested into it is false

  26.  * and vice versa.

  27.  *

  28.  * @since Ant 1.4

  29.  * @version $Revision: 1.6.2.4 $

  30.  */

  31. public class Not extends ConditionBase implements Condition {

  32. 

  33.     /**

  34.      * Evaluate condition

  35.      *

  36.      * @return true if the condition is true.

  37.      * @throws BuildException if the condition is not configured correctly.

  38.      */

  39.     public boolean eval() throws BuildException {

  40.         if (countConditions() > 1) {

  41.             throw new BuildException("You must not nest more than one "

  42.                 + "condition into <not>");

  43.         }

  44.         if (countConditions() < 1) {

  45.             throw new BuildException("You must nest a condition into <not>");

  46.         }

  47.         return !((Condition) getConditions().nextElement()).eval();

  48.     }

  49. 

  50. }