java.util.concurrent.ConcurrentMap Maven / Gradle / Ivy
/*
* Written by Doug Lea with assistance from members of JCP JSR-166
* Expert Group and released to the public domain, as explained at
* http://creativecommons.org/publicdomain/zero/1.0/
*/
package java.util.concurrent;
import java.util.Map;
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// removed link to collections framework docs
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/**
* A {@link java.util.Map} providing additional atomic
* {@code putIfAbsent}, {@code remove}, and {@code replace} methods.
*
* Memory consistency effects: As with other concurrent
* collections, actions in a thread prior to placing an object into a
* {@code ConcurrentMap} as a key or value
* happen-before
* actions subsequent to the access or removal of that object from
* the {@code ConcurrentMap} in another thread.
*
* @since 1.5
* @author Doug Lea
* @param the type of keys maintained by this map
* @param the type of mapped values
*/
public interface ConcurrentMap extends Map {
/**
* If the specified key is not already associated
* with a value, associate it with the given value.
* This is equivalent to
* {@code
* if (!map.containsKey(key))
* return map.put(key, value);
* else
* return map.get(key);}
*
* except that the action is performed atomically.
*
* @param key key with which the specified value is to be associated
* @param value value to be associated with the specified key
* @return the previous value associated with the specified key, or
* {@code null} if there was no mapping for the key.
* (A {@code null} return can also indicate that the map
* previously associated {@code null} with the key,
* if the implementation supports null values.)
* @throws UnsupportedOperationException if the {@code put} operation
* is not supported by this map
* @throws ClassCastException if the class of the specified key or value
* prevents it from being stored in this map
* @throws NullPointerException if the specified key or value is null,
* and this map does not permit null keys or values
* @throws IllegalArgumentException if some property of the specified key
* or value prevents it from being stored in this map
*/
V putIfAbsent(K key, V value);
/**
* Removes the entry for a key only if currently mapped to a given value.
* This is equivalent to
* {@code
* if (map.containsKey(key) && map.get(key).equals(value)) {
* map.remove(key);
* return true;
* } else
* return false;}
*
* except that the action is performed atomically.
*
* @param key key with which the specified value is associated
* @param value value expected to be associated with the specified key
* @return {@code true} if the value was removed
* @throws UnsupportedOperationException if the {@code remove} operation
* is not supported by this map
* @throws ClassCastException if the key or value is of an inappropriate
* type for this map
* (optional)
* @throws NullPointerException if the specified key or value is null,
* and this map does not permit null keys or values
* (optional)
*/
boolean remove(Object key, Object value);
/**
* Replaces the entry for a key only if currently mapped to a given value.
* This is equivalent to
* {@code
* if (map.containsKey(key) && map.get(key).equals(oldValue)) {
* map.put(key, newValue);
* return true;
* } else
* return false;}
*
* except that the action is performed atomically.
*
* @param key key with which the specified value is associated
* @param oldValue value expected to be associated with the specified key
* @param newValue value to be associated with the specified key
* @return {@code true} if the value was replaced
* @throws UnsupportedOperationException if the {@code put} operation
* is not supported by this map
* @throws ClassCastException if the class of a specified key or value
* prevents it from being stored in this map
* @throws NullPointerException if a specified key or value is null,
* and this map does not permit null keys or values
* @throws IllegalArgumentException if some property of a specified key
* or value prevents it from being stored in this map
*/
boolean replace(K key, V oldValue, V newValue);
/**
* Replaces the entry for a key only if currently mapped to some value.
* This is equivalent to
* {@code
* if (map.containsKey(key)) {
* return map.put(key, value);
* } else
* return null;}
*
* except that the action is performed atomically.
*
* @param key key with which the specified value is associated
* @param value value to be associated with the specified key
* @return the previous value associated with the specified key, or
* {@code null} if there was no mapping for the key.
* (A {@code null} return can also indicate that the map
* previously associated {@code null} with the key,
* if the implementation supports null values.)
* @throws UnsupportedOperationException if the {@code put} operation
* is not supported by this map
* @throws ClassCastException if the class of the specified key or value
* prevents it from being stored in this map
* @throws NullPointerException if the specified key or value is null,
* and this map does not permit null keys or values
* @throws IllegalArgumentException if some property of the specified key
* or value prevents it from being stored in this map
*/
V replace(K key, V value);
}