content: /* ===========================================================
   * JFreeChart : a free chart library for the Java(tm) platform
   * ===========================================================
   *
   * (C) Copyright 2000-2008, by Object Refinery Limited and Contributors.
   *
   * Project Info:  http://www.jfree.org/jfreechart/index.html
   *
   * This library is free software; you can redistribute it and/or modify it
   * under the terms of the GNU Lesser General Public License as published by
   * the Free Software Foundation; either version 2.1 of the License, or
   * (at your option) any later version.
   *
   * This library is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
   * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
   * License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
   * USA.
   *
   * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
   * in the United States and other countries.]
   *
   * ----------------
   * KeyedValues.java
   * ----------------
   * (C) Copyright 2002-2008, by Object Refinery Limited.
   *
   * Original Author:  David Gilbert (for Object Refinery Limited);
   * Contributor(s):   -;
   *
   * Changes:
   * --------
   * 23-Oct-2002 : Version 1 (DG);
   * 12-Jan-2005 : Updated Javadocs to specify new behaviour when key
   *               is not recognised (DG);
   * ------------- JFREECHART 1.0.0 ---------------------------------------------
   * 02-May-2006 : Updated API docs (DG);
   *
   */
  
  package org.jfree.data;
  
  import java.util.List;
  
  /**
   * An ordered list of (key, value) items where the keys are unique and
   * non-<code>null</code>.
   *
   * @see Values
   * @see DefaultKeyedValues
   */
  public interface KeyedValues extends Values {
  
      /**
       * Returns the key associated with the item at a given position.  Note
       * that some implementations allow re-ordering of the data items, so the
       * result may be transient.
       *
       * @param index  the item index (in the range <code>0</code> to
       *     <code>getItemCount() - 1</code>).
       *
       * @return The key (never <code>null</code>).
       *
       * @throws IndexOutOfBoundsException if <code>index</code> is not in the
       *     specified range.
       */
      public Comparable getKey(int index);
  
      /**
       * Returns the index for a given key.
       *
       * @param key  the key (<code>null</code> not permitted).
       *
       * @return The index, or <code>-1</code> if the key is unrecognised.
       *
       * @throws IllegalArgumentException if <code>key</code> is
       *     <code>null</code>.
       */
      public int getIndex(Comparable key);
  
      /**
       * Returns the keys for the values in the collection.  Note that you can
       * access the values in this collection by key or by index.  For this
       * reason, the key order is important - this method should return the keys
       * in order.  The returned list may be unmodifiable.
       *
       * @return The keys (never <code>null</code>).
       */
      public List getKeys();
  
      /**
       * Returns the value for a given key.
       *
       * @param key  the key.
       *
       * @return The value (possibly <code>null</code>).
       *
       * @throws UnknownKeyException if the key is not recognised.
       */
      public Number getValue(Comparable key);
  
  }
  