ConcurrentMap (Java Platform SE 7 b138)

Type Parameters:
K - the type of keys maintained by this map
V - the type of mapped values

All Superinterfaces:

Map<K,V>

All Known Subinterfaces:

ConcurrentNavigableMap<K,V>

All Known Implementing Classes:

ConcurrentHashMap, ConcurrentSkipListMap
```
public interface ConcurrentMap<K,V>
extends Map<K,V>
```
A Map providing additional atomic putIfAbsent, remove, and replace methods.
Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a ConcurrentMap as a key or value happen-before actions subsequent to the access or removal of that object from the ConcurrentMap in another thread.
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

Methods
Modifier and Type	Method and Description
`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)` Removes the entry for a key only if currently mapped to a given value.
`V`	`replace(K key, V value)` Replaces the entry for a key only if currently mapped to some value.
`boolean`	`replace(K key, V oldValue, V newValue)` Replaces the entry for a key only if currently mapped to a 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:
    the previous value associated with the specified key, or null if there was no mapping for the key. (A null return can also indicate that the map previously associated null with the 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
    
    NullPointerException - if the specified key or value is null, and this map does not permit null keys or values
    
    IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map
  - remove
```
boolean remove(Object key,
             Object value)
```
    Removes the entry for a key only if currently mapped to a given value. This is equivalent to
```
   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 expected to be associated with the specified key
    
    Returns:
    true if the value was removed
    
    Throws:
    
    UnsupportedOperationException - if the remove operation is not supported by this map
    
    ClassCastException - if the key or value is of an inappropriate type for this map (optional)
    
    NullPointerException - if the specified key or value is null, and this map does not permit null keys or values (optional)
  - replace
```
boolean replace(K key,
              V oldValue,
              V newValue)
```
    Replaces the entry for a key only if currently mapped to a given value. This is equivalent to
```
   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
    
    ClassCastException - if the class of a specified key or value prevents it from being stored in this map
    
    NullPointerException - if a specified key or value is null, and this map does not permit null keys or values
    
    IllegalArgumentException - if some property of a specified key or value prevents it from being stored in this map
  - replace
```
V replace(K key,
        V value)
```
    Replaces the entry for a key only if currently mapped to some value. This is equivalent to
```
   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:
    the previous value associated with the specified key, or null if there was no mapping for the key. (A null return can also indicate that the map previously associated null with the 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
    
    NullPointerException - if the specified key or value is null, and this map does not permit null keys or values
    
    IllegalArgumentException - if some property of the specified key or value prevents it from being stored in this map

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DRAFT ea-b138

Interface ConcurrentMap<K,V>

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.Map

Method Summary

Methods inherited from interface java.util.Map

Method Detail

putIfAbsent

remove

replace

replace