/*
 * @(#)ListResourceBundle.java	1.16 00/01/19
 *
 * Copyright 1996-2000 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */

/*
 * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
 * (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved
 *
 * The original version of this source code and documentation
 * is copyrighted and owned by Taligent, Inc., a wholly-owned
 * subsidiary of IBM. These materials are provided under terms
 * of a License Agreement between Taligent and Sun. This technology
 * is protected by multiple US and International patents.
 *
 * This notice and attribution to Taligent may not be removed.
 * Taligent is a registered trademark of Taligent, Inc.
 *
 */

package java.util;
import java.util.Hashtable;

/**
 * <code>ListResourceBundle</code> is a abstract subclass of
 * <code>ResourceBundle</code> that manages resources for a locale
 * in a convenient and easy to use list. See <code>ResourceBundle</code> for
 * more information about resource bundles in general.
 *
 * <P>
 * Subclasses must override <code>getContents</code> and provide an array,
 * where each item in the array is a pair of objects.
 * The first element of each pair is a <code>String</code> key, and the second
 * is the value associated with that key.  [Right now, there's no error-checking
 * code to enforce this, so you could specify key-value pairs that have
 * something other than a String as a key.  But since the interfaces are defined
 * in terms of String, any value with a key that isn't a String will be
 * inaccessible.]
 *
 * <p>
 * In the following example, the keys are of the form "s1"... The actual
 * keys are entirely up to your choice, so long as they are the same as
 * the keys you use in your program to retrieve the objects from the bundle.
 * Keys are case-sensitive. <code>MyResource</code> is the default version
 * of the bundle family, and <code>MyResource_fr</code> is the french version:
 * <blockquote>
 * <pre>
 * //====================
 * class MyResource extends ListResourceBundle {
 *  public Object[][] getContents() {
 *      return contents;
 *  }
 *  static final Object[][] contents = {
 *  // LOCALIZE THIS
 *      {"s1", "3"},        // starting value in choice field
 *      {"s2", "MyDisk"},    // starting value in string field
 *      {"s3", "3 Mar 96"}, // starting value in date field
 *      {"s4", "The disk '{1}' contained {0} on {2}."}, // initial pattern
 *      {"s5", "0"},        // first choice number
 *      {"s6", "no files"}, // first choice value
 *      {"s7", "1"},        // second choice number
 *      {"s8", "one file"}, // second choice value
 *      {"s9", "2"},        // third choice number
 *      {"s10", "{0}|3 files"}, // third choice value
 *      {"s11", "format threw an exception: {0}"},  // generic exception message
 *      {"s12", "ERROR"},   // what to show in field in case of error
 *      {"s14", "Result"},  // label for formatted stuff
 *      {"s13", "Dialog"},  // standard font
 *      {"s15", "Pattern"}, // label for standard pattern
 *      {"s16", new Dimension(1,5)} // real object, not just string
 *  // END OF MATERIAL TO LOCALIZE
 *  };
 * }
 * //====================
 * class MyResource_fr  extends ListResourceBundle {
 *  public Object[][] getContents() {
 *      return contents;
        }
 *  static final Object[][] contents = {
 *  // LOCALIZE THIS
 *      {"s1", "3"},        // starting value in choice field
 *      {"s2", "MonDisk"},  // starting value in string field
 *      {"s3", "3 Mar 96"}, // starting value in date field
 *      {"s4", "Le disk '{1}' a {0} a {2}."},   // initial pattern
 *      {"s5", "0"},        // first choice number
 *      {"s6", "pas de files"}, // first choice value
 *      {"s7", "1"},        // second choice number
 *      {"s8", "une file"}, // second choice value
 *      {"s9", "2"},        // third choice number
 *      {"s10", "{0}|3 files"}, // third choice value
 *      {"s11", "Le format a jete une exception: {0}"}, // generic exception message
 *      {"s12", "ERROR"},   // what to show in field in case of error
 *      {"s14", "Resulte"}, // label for formatted stuff
 *      {"s13", "Dialogue"},    // standard font
 *      {"s15", "Pattern"}, // label for standard pattern
 *      {"s16", new Dimension(1,3)} // real object, not just string
 *  // END OF MATERIAL TO LOCALIZE
 *  };
 * }
 * </pre>
 * </blockquote>
 * @see ResourceBundle
 * @see PropertyResourceBundle
 * @since JDK1.1
 */
public abstract class ListResourceBundle extends ResourceBundle {
    /**
     * Sole constructor.  (For invocation by subclass constructors, typically
     * implicit.)
     */
    public ListResourceBundle() {
    }

    /**
     * Override of ResourceBundle, same semantics
     */
    public final Object handleGetObject(String key) {
        // lazily load the lookup hashtable.
        if (lookup == null) {
            loadLookup();
        }
        return lookup.get(key); // this class ignores locales
    }

    /**
     * Implementation of ResourceBundle.getKeys.
     */
    public Enumeration getKeys() {
        // lazily load the lookup hashtable.
        if (lookup == null) {
            loadLookup();
        }
        Enumeration result = null;
        if (parent != null) {
            final Enumeration myKeys = lookup.keys();
            final Enumeration parentKeys = parent.getKeys();

            result = new Enumeration() {
                public boolean hasMoreElements() {
                    if (temp == null)
                        nextElement();
                    return temp != null;
                }

                public Object nextElement() {
                    Object returnVal = temp;
                    if (myKeys.hasMoreElements())
                        temp = myKeys.nextElement();
                    else {
                        temp = null;
                        while (temp == null && parentKeys.hasMoreElements()) {
                            temp = parentKeys.nextElement();
                            if (lookup.containsKey(temp))
                                temp = null;
                        }
                    }
                    return returnVal;
                }

                Object temp = null;
            };
        } else {
            result = lookup.keys();
        }
        return result;
    }

    /**
     * See class description.
     */
    abstract protected Object[][] getContents();

    // ==================privates====================

    /**
     * We lazily load the lookup hashtable.  This function does the
     * loading.
     */
    private synchronized void loadLookup() {
        if (lookup != null)
            return;

        Object[][] contents = getContents();
        Hashtable temp = new Hashtable(contents.length);
        for (int i = 0; i < contents.length; ++i) {
            temp.put(contents[i][0],contents[i][1]);
        }
        lookup = temp;
    }

    private Hashtable lookup = null;
}