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.util.Iterator;
  
  
  /**
   * A Cache let the user store key-value-pairs in a permanent manner and access
   * them.
   * It is possible that a client uses get() before load() therefore the
   * implementation must ensure that no error occurred because of the wrong
   * <i>order</i>.
   * The implementing class should implement a useful toString() method.
   *
   * @version 2003-09-13
   * @since  Ant 1.6
   */
  public interface Cache {
  
      /**
       * Checks its prerequisites.
       * @return <i>true</i> if all is ok, otherwise <i>false</i>.
       */
      boolean isValid();
  
      /** Deletes the cache. If file based the file has to be deleted also. */
      void delete();
  
      /** Loads the cache, must handle not existing cache. */
      void load();
  
      /** Saves modification of the cache. */
      void save();
  
      /**
       * Returns a value for a given key from the cache.
       * @param key the key
       * @return the stored value
       */
      Object get(Object key);
  
      /**
       * Saves a key-value-pair in the cache.
       * @param key the key
       * @param value the value
       */
      void put(Object key, Object value);
  
      /**
       * Returns an iterator over the keys in the cache.
       * @return An iterator over the keys.
       */
      Iterator<String> iterator();
  }
  