001/*
002 * Copyright (c) 1995, 2022, Oracle and/or its affiliates. All rights reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation.  Oracle designates this
008 * particular file as subject to the "Classpath" exception as provided
009 * by Oracle in the LICENSE file that accompanied this code.
010 *
011 * This code is distributed in the hope that it will be useful, but WITHOUT
012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
014 * version 2 for more details (a copy is included in the LICENSE file that
015 * accompanied this code).
016 *
017 * You should have received a copy of the GNU General Public License version
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019 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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021 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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023 * questions.
024 */
025package Torello.Java.ReadOnly;
026
027import java.util.Enumeration;
028
029/**
030 * Immutable variant of Java Collections Framework abstract class
031 * <CODE>java&#46;util&#46;Dictionary&lt;K, V&gt;</CODE>.
032 * 
033 * <EMBED CLASS='external-html' DATA-JDK=ReadOnlyDictionary DATA-FILE-ID=ABSTRACT_CLASS>
034 * 
035 * @param <K> the type of keys
036 * @param <V> the type of mapped values
037 */
038@Torello.JavaDoc.JDHeaderBackgroundImg(EmbedTagFileID="JDHBI_INTERFACE")
039public interface ReadOnlyDictionary<K, V>
040{
041    /**
042     * Returns the number of entries (distinct keys) in this dictionary.
043     * @return  the number of keys in this dictionary.
044     */
045    int size();
046
047    /**
048     * Tests if this dictionary maps no keys to value. The general contract for the {@code isEmpty}
049     * method is that the result is true if and only if this dictionary contains no entries.
050     *
051     * @return  {@code true} if this dictionary maps no keys to values; {@code false} otherwise.
052     */
053    boolean isEmpty();
054
055    /**
056     * Returns an enumeration of the keys in this dictionary. The general contract for the keys
057     * method is that an {@code Enumeration} object is returned that will generate all the keys for
058     * which this dictionary contains entries.
059     *
060     * @return  an enumeration of the keys in this dictionary.
061     * @see #elements()
062     */
063    Enumeration<K> keys();
064
065    /**
066     * Returns an enumeration of the values in this dictionary. The general contract for the
067     * {@code elements} method is that an {@code Enumeration} is returned that will generate all
068     * the elements contained in entries in this dictionary.
069     *
070     * @return an enumeration of the values in this dictionary.
071     * @see #keys()
072     */
073    Enumeration<V> elements();
074
075    /**
076     * Returns the value to which the key is mapped in this dictionary.  The general contract for
077     * the {@code isEmpty} method is that if this dictionary contains an entry for the specified
078     * key, the associated value is returned; otherwise, {@code null} is returned.
079     *
080     * @return the value to which the key is mapped in this dictionary;
081     * 
082     * @param key a key in this dictionary.  {@code null} if the key is not mapped to any value
083     * in this dictionary.
084     * 
085     * @throws NullPointerException if the {@code key} is {@code null}.
086     */
087    V get(Object key);
088}