content: /*
   *  Licensed to the Apache Software Foundation (ASF) under one or more
   *  contributor license agreements.  See the NOTICE file distributed with
   *  this work for additional information regarding copyright ownership.
   *  The ASF licenses this file to You under the Apache License, Version 2.0
   *  (the "License"); you may not use this file except in compliance with
   *  the License.  You may obtain a copy of the License at
   *
   *      https://www.apache.org/licenses/LICENSE-2.0
   *
   *  Unless required by applicable law or agreed to in writing, software
   *  distributed under the License is distributed on an "AS IS" BASIS,
   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *  See the License for the specific language governing permissions and
   *  limitations under the License.
   *
   */
  
  package org.apache.tools.ant.taskdefs.condition;
  
  import org.apache.tools.ant.BuildException;
  
  /**
   * &lt;not&gt; condition.
   *
   * Evaluates to true if the single condition nested into it is false
   * and vice versa.
   *
   * @since Ant 1.4
   */
  public class Not extends ConditionBase implements Condition {
  
      /**
       * Evaluate condition
       *
       * @return true if the condition is true.
       * @throws BuildException if the condition is not configured correctly.
       */
      @Override
      public boolean eval() throws BuildException {
          if (countConditions() > 1) {
              throw new BuildException(
                  "You must not nest more than one condition into <not>");
          }
          if (countConditions() < 1) {
              throw new BuildException("You must nest a condition into <not>");
          }
          return !getConditions().nextElement().eval();
      }
  
  }
  