ConcurrentMap (Java 2 Platform SE 5.0) (original) (raw)

java.util.concurrent

Interface ConcurrentMap<K,V>

Type Parameters:

K - the type of keys maintained by this map

V - the type of mapped values

All Superinterfaces:

Map<K,V>

All Known Implementing Classes:

ConcurrentHashMap

public interface ConcurrentMap<K,V>

extends Map<K,V>

A Map providing additional atomicputIfAbsent, remove, and replace methods.

This interface is a member of the Java Collections Framework.

Since:

1.5

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.Map
Map.Entry<K,V>

Method Summary
V	[putIfAbsent](../../../java/util/concurrent/ConcurrentMap.html#putIfAbsent%28K, V%29)(K key,V value) If the specified key is not already associated with a value, associate it with the given value.
boolean	[remove](../../../java/util/concurrent/ConcurrentMap.html#remove%28java.lang.Object, java.lang.Object%29)(Object key,Object value) Remove entry for key only if currently mapped to given value.
V	[replace](../../../java/util/concurrent/ConcurrentMap.html#replace%28K, V%29)(K key,V value) Replace entry for key only if currently mapped to some value.
boolean	[replace](../../../java/util/concurrent/ConcurrentMap.html#replace%28K, V, V%29)(K key,V oldValue,V newValue) Replace entry for key only if currently mapped to given value.

Methods inherited from interface java.util.Map
clear, containsKey, containsValue, entrySet, equals, get, hashCode, isEmpty, keySet, [put](../../../java/util/Map.html#put%28K, V%29), putAll, remove, size, values

Method Detail

putIfAbsent

V putIfAbsent(K key, V value)

If the specified key is not already associated with a value, associate it with the given value. This is equivalent to

if (!map.containsKey(key)) return map.put(key, value); else return map.get(key);

Except that the action is performed atomically.

Parameters:

key - key with which the specified value is to be associated.

value - value to be associated with the specified key.

Returns:

previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key, if the implementation supportsnull values.

Throws:

[UnsupportedOperationException](../../../java/lang/UnsupportedOperationException.html "class in java.lang") - if the put operation is not supported by this map.

[ClassCastException](../../../java/lang/ClassCastException.html "class in java.lang") - if the class of the specified key or value prevents it from being stored in this map.

[IllegalArgumentException](../../../java/lang/IllegalArgumentException.html "class in java.lang") - if some aspect of this key or value prevents it from being stored in this map.

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if this map does not permit null keys or values, and the specified key or value isnull.

remove

boolean remove(Object key, Object value)

Remove entry for key only if currently mapped to given value. Acts as

if ((map.containsKey(key) && map.get(key).equals(value)) { map.remove(key); return true; } else return false;

except that the action is performed atomically.

Parameters:

key - key with which the specified value is associated.

value - value associated with the specified key.

Returns:

true if the value was removed, false otherwise

Throws:

[UnsupportedOperationException](../../../java/lang/UnsupportedOperationException.html "class in java.lang") - if the remove operation is not supported by this map.

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if this map does not permit null keys or values, and the specified key or value isnull.

replace

boolean replace(K key, V oldValue, V newValue)

Replace entry for key only if currently mapped to given value. Acts as

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.

Parameters:

key - key with which the specified value is associated.

oldValue - value expected to be associated with the specified key.

newValue - value to be associated with the specified key.

Returns:

true if the value was replaced

Throws:

[UnsupportedOperationException](../../../java/lang/UnsupportedOperationException.html "class in java.lang") - if the put operation is not supported by this map.

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if this map does not permit null keys or values, and the specified key or value isnull.

replace

V replace(K key, V value)

Replace entry for key only if currently mapped to some value. Acts as

if ((map.containsKey(key)) { return map.put(key, value); } else return null;

except that the action is performed atomically.

Parameters:

key - key with which the specified value is associated.

value - value to be associated with the specified key.

Returns:

Throws:

[UnsupportedOperationException](../../../java/lang/UnsupportedOperationException.html "class in java.lang") - if the put operation is not supported by this map.

[NullPointerException](../../../java/lang/NullPointerException.html "class in java.lang") - if this map does not permit null keys or values, and the specified key or value isnull.

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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.