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/*
 * Copyright (c) 1995, 2022, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package Torello.Java.ReadOnly;

import java.util.Enumeration;

/**
 * Immutable variant of Java Collections Framework abstract class
 * <CODE>java&#46;util&#46;Dictionary&lt;K, V&gt;</CODE>.
 * 
 * <EMBED CLASS='external-html' DATA-JDK=ReadOnlyDictionary DATA-FILE-ID=ABSTRACT_CLASS>
 * 
 * @param <K> the type of keys
 * @param <V> the type of mapped values
 */
@Torello.JavaDoc.JDHeaderBackgroundImg(EmbedTagFileID="JDHBI_INTERFACE")
public interface ReadOnlyDictionary<K, V>
{
    /**
     * Returns the number of entries (distinct keys) in this dictionary.
     * @return  the number of keys in this dictionary.
     */
    int size();

    /**
     * Tests if this dictionary maps no keys to value. The general contract for the {@code isEmpty}
     * method is that the result is true if and only if this dictionary contains no entries.
     *
     * @return  {@code true} if this dictionary maps no keys to values; {@code false} otherwise.
     */
    boolean isEmpty();

    /**
     * Returns an enumeration of the keys in this dictionary. The general contract for the keys
     * method is that an {@code Enumeration} object is returned that will generate all the keys for
     * which this dictionary contains entries.
     *
     * @return  an enumeration of the keys in this dictionary.
     * @see #elements()
     */
    Enumeration<K> keys();

    /**
     * Returns an enumeration of the values in this dictionary. The general contract for the
     * {@code elements} method is that an {@code Enumeration} is returned that will generate all
     * the elements contained in entries in this dictionary.
     *
     * @return an enumeration of the values in this dictionary.
     * @see #keys()
     */
    Enumeration<V> elements();

    /**
     * Returns the value to which the key is mapped in this dictionary.  The general contract for
     * the {@code isEmpty} method is that if this dictionary contains an entry for the specified
     * key, the associated value is returned; otherwise, {@code null} is returned.
     *
     * @return the value to which the key is mapped in this dictionary;
     * 
     * @param key a key in this dictionary.  {@code null} if the key is not mapped to any value
     * in this dictionary.
     * 
     * @throws NullPointerException if the {@code key} is {@code null}.
     */
    V get(Object key);
}