AbstractMapEntry.java

  1. /*
  2.  * Licensed to the Apache Software Foundation (ASF) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * The ASF licenses this file to You under the Apache License, Version 2.0
  6.  * (the "License"); you may not use this file except in compliance with
  7.  * the License.  You may obtain a copy of the License at
  8.  *
  9.  *      http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  17. package org.apache.commons.collections4.keyvalue;

  18. import java.util.Map;
  19. import java.util.Objects;

  20. /**
  21.  * Abstract Pair class to assist with creating correct
  22.  * {@link java.util.Map.Entry Map.Entry} implementations.
  23.  *
  24.  * @param <K> the type of keys
  25.  * @param <V> the type of mapped values
  26.  * @since 3.0
  27.  */
  28. public abstract class AbstractMapEntry<K, V> extends AbstractKeyValue<K, V> implements Map.Entry<K, V> {

  29.     /**
  30.      * Constructs a new entry with the given key and given value.
  31.      *
  32.      * @param key  the key for the entry, may be null
  33.      * @param value  the value for the entry, may be null
  34.      */
  35.     protected AbstractMapEntry(final K key, final V value) {
  36.         super(key, value);
  37.     }

  38.     /**
  39.      * Compares this {@code Map.Entry} with another {@code Map.Entry}.
  40.      * <p>
  41.      * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)}
  42.      *
  43.      * @param obj  the object to compare to
  44.      * @return true if equal key and value
  45.      */
  46.     @Override
  47.     public boolean equals(final Object obj) {
  48.         if (obj == this) {
  49.             return true;
  50.         }
  51.         if (!(obj instanceof Map.Entry)) {
  52.             return false;
  53.         }
  54.         final Map.Entry<?, ?> other = (Map.Entry<?, ?>) obj;
  55.         return Objects.equals(getKey(), other.getKey()) &&
  56.                Objects.equals(getValue(), other.getValue());
  57.     }

  58.     /**
  59.      * Gets a hashCode compatible with the equals method.
  60.      * <p>
  61.      * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}
  62.      *
  63.      * @return a suitable hash code
  64.      */
  65.     @Override
  66.     public int hashCode() {
  67.         return (getKey() == null ? 0 : getKey().hashCode()) ^
  68.                (getValue() == null ? 0 : getValue().hashCode());
  69.     }

  70.     /**
  71.      * Sets the value stored in this {@code Map.Entry}.
  72.      * <p>
  73.      * This {@code Map.Entry} is not connected to a Map, so only the
  74.      * local data is changed.
  75.      *
  76.      * @param value  the new value
  77.      * @return the previous value
  78.      */
  79.     @Override
  80.     public V setValue(final V value) { // NOPMD
  81.         return super.setValue(value);
  82.     }

  83. }