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 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
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 *  distributed under the License is distributed on an "AS IS" BASIS,
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package java.util;


/**
 * A {@code Map} is a data structure consisting of a set of keys and values
 * in which each key is mapped to a single value.  The class of the objects
 * used as keys is declared when the {@code Map} is declared, as is the
 * class of the corresponding values.
 * 

* A {@code Map} provides helper methods to iterate through all of the * keys contained in it, as well as various methods to access and update * the key/value pairs. */ public interface Map { /** * {@code Map.Entry} is a key/value mapping contained in a {@code Map}. */ public static interface Entry { /** * Compares the specified object to this {@code Map.Entry} and returns if they * are equal. To be equal, the object must be an instance of {@code Map.Entry} and have the * same key and value. * * @param object * the {@code Object} to compare with this {@code Object}. * @return {@code true} if the specified {@code Object} is equal to this * {@code Map.Entry}, {@code false} otherwise. * @see #hashCode() */ public boolean equals(Object object); /** * Returns the key. * * @return the key */ public K getKey(); /** * Returns the value. * * @return the value */ public V getValue(); /** * Returns an integer hash code for the receiver. {@code Object} which are * equal return the same value for this method. * * @return the receiver's hash code. * @see #equals(Object) */ public int hashCode(); /** * Sets the value of this entry to the specified value, replacing any * existing value. * * @param object * the new value to set. * @return object the replaced value of this entry. */ public V setValue(V object); }; /** * Removes all elements from this {@code Map}, leaving it empty. * * @throws UnsupportedOperationException * if removing elements from this {@code Map} is not supported. * @see #isEmpty() * @see #size() */ public void clear(); /** * Returns whether this {@code Map} contains the specified key. * * @param key * the key to search for. * @return {@code true} if this map contains the specified key, * {@code false} otherwise. */ public boolean containsKey(Object key); /** * Returns whether this {@code Map} contains the specified value. * * @param value * the value to search for. * @return {@code true} if this map contains the specified value, * {@code false} otherwise. */ public boolean containsValue(Object value); /** * Returns a {@code Set} containing all of the mappings in this {@code Map}. Each mapping is * an instance of {@link Map.Entry}. As the {@code Set} is backed by this {@code Map}, * changes in one will be reflected in the other. * * @return a set of the mappings */ public Set> entrySet(); /** * Compares the argument to the receiver, and returns {@code true} if the * specified object is a {@code Map} and both {@code Map}s contain the same mappings. * * @param object * the {@code Object} to compare with this {@code Object}. * @return boolean {@code true} if the {@code Object} is the same as this {@code Object} * {@code false} if it is different from this {@code Object}. * @see #hashCode() * @see #entrySet() */ public boolean equals(Object object); /** * Returns the value of the mapping with the specified key. * * @param key * the key. * @return the value of the mapping with the specified key, or {@code null} * if no mapping for the specified key is found. */ public V get(Object key); /** * Returns an integer hash code for the receiver. {@code Object}s which are equal * return the same value for this method. * * @return the receiver's hash. * @see #equals(Object) */ public int hashCode(); /** * Returns whether this map is empty. * * @return {@code true} if this map has no elements, {@code false} * otherwise. * @see #size() */ public boolean isEmpty(); /** * Returns a set of the keys contained in this {@code Map}. The {@code Set} is backed by * this {@code Map} so changes to one are reflected by the other. The {@code Set} does not * support adding. * * @return a set of the keys. */ public Set keySet(); /** * Maps the specified key to the specified value. * * @param key * the key. * @param value * the value. * @return the value of any previous mapping with the specified key or * {@code null} if there was no mapping. * @throws UnsupportedOperationException * if adding to this {@code Map} is not supported. * @throws ClassCastException * if the class of the key or value is inappropriate for * this {@code Map}. * @throws IllegalArgumentException * if the key or value cannot be added to this {@code Map}. * @throws NullPointerException * if the key or value is {@code null} and this {@code Map} does * not support {@code null} keys or values. */ public V put(K key, V value); /** * Copies every mapping in the specified {@code Map} to this {@code Map}. * * @param map * the {@code Map} to copy mappings from. * @throws UnsupportedOperationException * if adding to this {@code Map} is not supported. * @throws ClassCastException * if the class of a key or a value of the specified {@code Map} is * inappropriate for this {@code Map}. * @throws IllegalArgumentException * if a key or value cannot be added to this {@code Map}. * @throws NullPointerException * if a key or value is {@code null} and this {@code Map} does not * support {@code null} keys or values. */ public void putAll(Map map); /** * Removes a mapping with the specified key from this {@code Map}. * * @param key * the key of the mapping to remove. * @return the value of the removed mapping or {@code null} if no mapping * for the specified key was found. * @throws UnsupportedOperationException * if removing from this {@code Map} is not supported. */ public V remove(Object key); /** * Returns the number of mappings in this {@code Map}. * * @return the number of mappings in this {@code Map}. */ public int size(); /** * Returns a {@code Collection} of the values contained in this {@code Map}. The {@code Collection} * is backed by this {@code Map} so changes to one are reflected by the other. The * {@code Collection} supports {@link Collection#remove}, {@link Collection#removeAll}, * {@link Collection#retainAll}, and {@link Collection#clear} operations, * and it does not support {@link Collection#add} or {@link Collection#addAll} operations. *

* This method returns a {@code Collection} which is the subclass of * {@link AbstractCollection}. The {@link AbstractCollection#iterator} method of this subclass returns a * "wrapper object" over the iterator of this {@code Map}'s {@link #entrySet()}. The {@link AbstractCollection#size} method * wraps this {@code Map}'s {@link #size} method and the {@link AbstractCollection#contains} method wraps this {@code Map}'s * {@link #containsValue} method. *

* The collection is created when this method is called at first time and * returned in response to all subsequent calls. This method may return * different Collection when multiple calls to this method, since it has no * synchronization performed. * * @return a collection of the values contained in this map. */ public Collection values(); }





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