package javolution37.javolution.util;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
import javolution37.javolution.realtime.LocalContext;
import javolution37.javolution.realtime.LocalReference;
/**
* This class represents a map which can be temporarily modified
* without impacting other threads ({@link LocalContext locally}
* scoped changes).
*
* Operation on instances of this class are completely thread-safe.
* For example:
* public class XmlFormat {
* static LocalMap CLASS_TO_FORMAT = new LocalMap();
* public static void setFormat(Class forClass, XmlFormat that) {
* CLASS_TO_FORMAT.put(forClass, that); // No synchronization required.
* }
* public static XmlFormat getInstance(Class forClass) {
* return CLASS_TO_FORMAT.get(forClass); // No synchronization required.
* }
* }
* public void main(String[] args) {
* // Sets default (global settings).
* XmlFormat.setFormat(Foo.class, xFormat);
* XmlFormat.setFormat(Bar.class, yFormat);
* }
* ... // Another thread.
* LocalContext.enter();
* try { // Use of local context to avoid impacting other threads.
* XmlFormat.setFormat(Foo.class, zFormat);
* XmlFormat.getInstance(Foo.class); // Returns zFormat
* XmlFormat.getInstance(Bar.class); // Returns yFormat (inherited)
* } finally {
* LocalContext.exit();
* }
* getInstance(Foo.class); // Returns xFormat
* [/code]
*
* Note: Because key-value mappings are inherited, the semantic of
* {@link #remove} and {@link #clear} is slightly modified (associate
* null values instead of removing the entries).
*
* @author Jean-Marie Dautelle
* @version 3.7, January 27, 2005
*/
public final class LocalMap implements Map {
/**
* Holds the fast map reference (shared map).
*/
private final LocalReference _mapRef = new LocalReference(new FastMap().setShared(true));
/**
* Default constructor.
*/
public LocalMap() {
}
/**
* Sets the key comparator for this local map.
*
* @param keyComparator the key comparator.
* @return this
*/
public LocalMap setKeyComparator(FastComparator keyComparator) {
localMap().setKeyComparator(keyComparator);
return this;
}
/**
* Sets the value comparator for this local map.
*
* @param valueComparator the value comparator.
* @return this
*/
public LocalMap setValueComparator(FastComparator valueComparator) {
localMap().setValueComparator(valueComparator);
return this;
}
/**
* Sets the default value for the specified key (typically done at
* initialization).
*
* @param key the key with which the specified value is to be associated.
* @param defaultValue the default value to be associated with the
* specified key.
* @return the previous default 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.
* @throws NullPointerException if the key is null.
*/
public V putDefault( K key, V defaultValue) {
return ( V ) ((FastMap) _mapRef.getDefault()).put(key,
defaultValue);
}
/**
* Returns the number of key-value mappings in this map.
*
* @return this map's size.
*/
public int size() {
return ((FastMap) _mapRef.get()).size();
}
/**
* Indicates if this map contains no key-value mappings.
*
* @return true if this map contains no key-value mappings;
* false otherwise.
*/
public boolean isEmpty() {
return ((FastMap) _mapRef.get()).isEmpty();
}
/**
* Indicates if this map contains a mapping for the specified key.
*
* @param key the key whose presence in this map is to be tested.
* @return true if this map contains a mapping for the
* specified key; false otherwise.
* @throws NullPointerException if the key is null.
*/
public boolean containsKey(Object key) {
return ((FastMap) _mapRef.get()).containsKey(key);
}
/**
* Indicates if this map associates one or more keys to the
* specified value.
*
* @param value the value whose presence in this map is to be tested.
* @return true if this map maps one or more keys to the
* specified value.
* @throws NullPointerException if the key is null.
*/
public boolean containsValue(Object value) {
return ((FastMap) _mapRef.get()).containsValue(value);
}
/**
* Returns the value to which this map associates the specified key.
*
* @param key the key whose associated value is to be returned.
* @return the value to which this map maps the specified key, or
* null if there is no mapping for the key.
* @throws NullPointerException if key is null.
*/
public V get(Object key) {
return ( V ) ((FastMap) _mapRef.get()).get(key);
}
/**
* Associates the specified value with the specified key in this map.
*
* @param key the key with which the specified value is to be associated.
* @param value the value to be associated with the specified key.
* @return the 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.
* @throws NullPointerException if the key is null.
*/
public V put( K key, V value) {
return ( V ) localMap().put(key, value);
}
/**
* Copies all of the mappings from the specified map to this map.
*
* @param map the mappings to be stored in this map.
* @throws NullPointerException the specified map is null,
* or the specified map contains null keys.
*/
public void putAll(Map map) {
localMap().putAll(map);
}
/**
* Removes the mapping for this key from this map if present
* (sets the local value to null).
*
* @param key the key whose value is set to null
* @return put(key, null)
* @throws NullPointerException if the key is null.
*/
public V remove(Object key) {
return put(( K )key, null);
}
/**
* Removes all mappings from this map (sets the local values to
* null).
*/
public void clear() {
FastMap localMap = localMap();
for (FastMap.Entry e = localMap.head(), end = localMap.tail(); (e = (FastMap.Entry) e.getNext()) != end;) {
e.setValue(null);
}
}
/**
* Returns a {@link FastCollection} view of the keys contained in this map.
*
* @return a set view of the keys contained in this map
* (instance of {@link FastCollection}).
*/
public Set keySet() {
return localMap().keySet();
}
/**
* Returns a {@link FastCollection} view of the values contained in this
* map.
*
* @return a collection view of the values contained in this map
* (instance of {@link FastCollection}).
*/
public Collection values() {
return localMap().values();
}
/**
* Returns a {@link FastCollection} view of the mappings contained in this
* map.
*
* @return a collection view of the mappings contained in this map
* (instance of {@link FastCollection}).
*/
public Set > entrySet() {
return localMap().entrySet();
}
/**
* Returns the local map or creates one on the stack and populates
* it from inherited settings.
*
* @return a shared fast map belonging to the current local context.
*/
private FastMap localMap() {
FastMap localMap = (FastMap) _mapRef.getLocal();
return (localMap != null) ? localMap : newLocalMap();
}
private FastMap newLocalMap() {
FastMap parentMap = (FastMap) _mapRef.get();
FastMap localMap = FastMap.newInstance();
localMap.setShared(true);
localMap.setKeyComparator(parentMap.getKeyComparator());
localMap.setValueComparator(parentMap.getValueComparator());
localMap.putAll(parentMap);
_mapRef.set(localMap);
return localMap;
}
}
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