    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.Map;
    021import java.util.Set;
    022
    023/**
    024 * The "read" subset of the {@link Map} interface.
    025 *
    026 * @param <K> the type of the keys in this map
    027 * @param <V> the type of the values in this map
    028 * @since 4.0
    029 * @see Put
    030 */
    031public interface Get<K, V> {
    032
    033    /**
    034     * Tests for presence of a given key.
    035     *
    036     * @param key key whose presence in this map is to be tested
    037     * @return {@code true} if this map contains a mapping for the specified key
    038     * @see Map#containsKey(Object)
    039     */
    040    boolean containsKey(Object key);
    041
    042    /**
    043     * Tests for presence of a given value.
    044     *
    045     * @param value value whose presence in this map is to be tested
    046     * @return {@code true} if this map maps one or more keys to the specified value
    047     * @see Map#containsValue(Object)
    048     */
    049    boolean containsValue(Object value);
    050
    051    /**
    052     * Gets a set view of the mappings contained in this map.
    053     *
    054     * @return a set view of the mappings contained in this map.
    055     * @see Map#entrySet()
    056     */
    057    Set<Map.Entry<K, V>> entrySet();
    058
    059    /**
    060     * Gets a value at a given key.
    061     *
    062     * @param key the key whose associated value is to be returned
    063     * @return the value to which the specified key is mapped, or {@code null} if this map contains no mapping for the key
    064     * @see Map#get(Object)
    065     */
    066    V get(Object key);
    067
    068    /**
    069     * Tests whether this instance contains any key-value mappings.
    070     *
    071     * @return {@code true} if this map contains no key-value mappings
    072     * @see Map#isEmpty()
    073     */
    074    boolean isEmpty();
    075
    076    /**
    077     * Gets a view of the keys contained in this map.
    078     *
    079     * @return a set view of the keys contained in this map
    080     * @see Map#keySet()
    081     */
    082    Set<K> keySet();
    083
    084    /**
    085     * Remove a key-value mappings.
    086     *
    087     * @param key key whose mapping is to be removed from the map
    088     * @return the previous value associated with {@code key}, or {@code null} if there was no mapping for {@code key}.
    089     * @see Map#remove(Object)
    090     */
    091    V remove(Object key);
    092
    093    /**
    094     * Gets the number of key-value mappings in this map.
    095     *
    096     * @return the number of key-value mappings in this map.
    097     * @see Map#size()
    098     */
    099    int size();
    100
    101    /**
    102     * Gets a a collection view of the values contained in this map.
    103     *
    104     * @return a collection view of the values contained in this map.
    105     * @see Map#values()
    106     */
    107    Collection<V> values();
    108
    109}