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.types.selectors.modifiedselector;
  
  import java.io.File;
  
  /**
   * Computes a 'timestamp' of file based on the lastModified time of that file.
   *
   * @version 2018-07-25
   * @since  Ant 1.10.6 and 1.9.14
   */
  public class LastModifiedAlgorithm implements Algorithm {
  
      /**
       * This algorithm doesn't need any configuration.
       * Therefore it's always valid.
       * @return always true
       */
      public boolean isValid() {
          return true;
      }
  
      /**
       * Computes a 'timestamp' for a file based on the lastModified time.
       * @param file  The file for which the value should be computed
       * @return the timestamp or <i>null</i> if the timestamp couldn't be computed
       */
      public String getValue(File file) {
          long lastModified = file.lastModified();
          if (lastModified == 0L) {
              return null;
          }
  
          return Long.toString(lastModified);
      }
  }
  