    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.collections4;
    018
    019import java.util.Collection;
    020import java.util.Set;
    021
    022/**
    023 * The "read" subset of the {@link java.util.Map} interface.
    024 *
    025 * @param <K> the type of the keys in this map
    026 * @param <V> the type of the values in this map
    027 *
    028 * @since 4.0
    029 * @see Put
    030 */
    031public interface Get<K, V> {
    032
    033    /**
    034     * @param key key whose presence in this map is to be tested
    035     * @return {@code true} if this map contains a mapping for the specified
    036     *         key
    037     * @see java.util.Map#containsKey(Object)
    038     */
    039    boolean containsKey(Object key);
    040
    041    /**
    042     * @param value value whose presence in this map is to be tested
    043     * @return {@code true} if this map maps one or more keys to the
    044     *         specified value
    045     * @see java.util.Map#containsValue(Object)
    046     */
    047    boolean containsValue(Object value);
    048
    049    /**
    050     * @return a set view of the mappings contained in this map
    051     * @see java.util.Map#entrySet()
    052     */
    053    Set<java.util.Map.Entry<K, V>> entrySet();
    054
    055    /**
    056     * @param key the key whose associated value is to be returned
    057     * @return the value to which the specified key is mapped, or
    058     *         {@code null} if this map contains no mapping for the key
    059     * @see java.util.Map#get(Object)
    060     */
    061    V get(Object key);
    062
    063    /**
    064     * @return {@code true} if this map contains no key-value mappings
    065     * @see java.util.Map#isEmpty()
    066     */
    067    boolean isEmpty();
    068
    069    /**
    070     * @return a set view of the keys contained in this map
    071     * @see java.util.Map#keySet()
    072     */
    073    Set<K> keySet();
    074
    075    /**
    076     * @param key key whose mapping is to be removed from the map
    077     * @return the previous value associated with {@code key}, or
    078     *         {@code null} if there was no mapping for {@code key}.
    079     * @see java.util.Map#remove(Object)
    080     */
    081    V remove(Object key);
    082
    083    /**
    084     * @return the number of key-value mappings in this map
    085     * @see java.util.Map#size()
    086     */
    087    int size();
    088
    089    /**
    090     * @return a collection view of the values contained in this map
    091     * @see java.util.Map#values()
    092     */
    093    Collection<V> values();
    094
    095}