org.opencms.util

Class CmsNullIgnoringConcurrentMap<K,V>

java.lang.Object

org.opencms.util.CmsNullIgnoringConcurrentMap<K,V>

Type Parameters:

K - the key type

V - the value type

All Implemented Interfaces:

java.util.Map<K,V>

public class CmsNullIgnoringConcurrentMap<K,V>
extends java.lang.Object
implements java.util.Map<K,V>

Wrapper around ConcurrentHashMap which allows null values.

The point of this is the following: Often, HashMaps in older code are accessed concurrently by multiple threads. When these threads modify the map concurrently, an infinite loop may occur due to the standard HashMap implementation. But sometimes we can't just replace the HashMap with a ConcurrentHashMap because that class doesn't allow null values and we don't always know for certain whether null values are used or not. But if we don't care about the distinction about null values and entries not being present, we can use this map class which will just log an error and remove the entry when trying to set a null value. NOTE: Currently this wrapper does *not* check value modifications made to entries returned by entrySet!

Nested Class Summary

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

java.util.Map.Entry<K,V>

Constructor Summary

Constructors

Constructor and Description
CmsNullIgnoringConcurrentMap() Creates a new instance.
CmsNullIgnoringConcurrentMap(java.util.Map<K,V> otherMap) Creates a new instance from another map.

Method Summary

Methods

Modifier and Type	Method and Description
void	clear()
boolean	containsKey(java.lang.Object key)
boolean	containsValue(java.lang.Object value)
java.util.Set<java.util.Map.Entry<K,V>>	entrySet()
boolean	equals(java.lang.Object o)
V	get(java.lang.Object key)
int	hashCode()
boolean	isEmpty()
java.util.Set<K>	keySet()
V	put(K key, V value) Sets the given map value for the given key, unless either of them is null.
void	putAll(java.util.Map<? extends K,? extends V> m)
V	remove(java.lang.Object key)
int	size()
java.util.Collection<V>	values()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CmsNullIgnoringConcurrentMap

public CmsNullIgnoringConcurrentMap()

Creates a new instance.

CmsNullIgnoringConcurrentMap

public CmsNullIgnoringConcurrentMap(java.util.Map<K,V> otherMap)

Creates a new instance from another map.

Parameters:

otherMap - the other map

Method Detail

clear

public void clear()

Specified by:

clear in interface java.util.Map<K,V>

See Also:

Map.clear()

containsKey

public boolean containsKey(java.lang.Object key)

Specified by:

containsKey in interface java.util.Map<K,V>

See Also:

Map.containsKey(java.lang.Object)

containsValue

public boolean containsValue(java.lang.Object value)

Specified by:

containsValue in interface java.util.Map<K,V>

See Also:

Map.containsValue(java.lang.Object)

entrySet

public java.util.Set<java.util.Map.Entry<K,V>> entrySet()

Specified by:

entrySet in interface java.util.Map<K,V>

See Also:

Map.entrySet()

equals

public boolean equals(java.lang.Object o)

Specified by:

equals in interface java.util.Map<K,V>

Overrides:

equals in class java.lang.Object

See Also:

Map.equals(java.lang.Object)

get

public V get(java.lang.Object key)

Specified by:

get in interface java.util.Map<K,V>

See Also:

Map.get(java.lang.Object)

hashCode

public int hashCode()

Specified by:

hashCode in interface java.util.Map<K,V>

Overrides:

hashCode in class java.lang.Object

See Also:

Map.hashCode()

isEmpty

public boolean isEmpty()

Specified by:

isEmpty in interface java.util.Map<K,V>

See Also:

Map.isEmpty()

keySet

public java.util.Set<K> keySet()

Specified by:

keySet in interface java.util.Map<K,V>

See Also:

Map.keySet()

put

public V put(K key,
    V value)

Sets the given map value for the given key, unless either of them is null.

If the value is null,

Specified by:

put in interface java.util.Map<K,V>

Parameters:

key - the key

value - the value

Returns:

the old value

See Also:

Map.put(java.lang.Object, java.lang.Object)

putAll

public void putAll(java.util.Map<? extends K,? extends V> m)

Specified by:

putAll in interface java.util.Map<K,V>

See Also:

Map.putAll(java.util.Map)

remove

public V remove(java.lang.Object key)

Specified by:

remove in interface java.util.Map<K,V>

See Also:

Map.remove(java.lang.Object)

size

public int size()

Specified by:

size in interface java.util.Map<K,V>

See Also:

Map.size()

values

public java.util.Collection<V> values()

Specified by:

values in interface java.util.Map<K,V>

See Also:

Map.values()