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 atomic putIfAbsent , 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 ( K  key, V  value)           If the specified key is not already associated with a value, associate it with the given value.
boolean	remove ( Object  key, Object  value)           Remove entry for key only if currently mapped to given value.
V	replace ( K  key, V  value)           Replace entry for key only if currently mapped to some value.
boolean	replace ( 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 , 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 supports null values.

Throws:

UnsupportedOperationException - if the put operation is not supported by this map.

ClassCastException - if the class of the specified key or value prevents it from being stored in this map.

IllegalArgumentException - if some aspect of this key or value prevents it from being stored in this map.

NullPointerException - if this map does not permit null keys or values, and the specified key or value is null .

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 - if the remove operation is not supported by this map.

NullPointerException - if this map does not permit null keys or values, and the specified key or value is null .

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 - if the put operation is not supported by this map.

NullPointerException - if this map does not permit null keys or values, and the specified key or value is null .

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:

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 supports null values.

Throws:

UnsupportedOperationException - if the put operation is not supported by this map.

NullPointerException - if this map does not permit null keys or values, and the specified key or value is null .