nl.nn.xmldecoder.finder.WeakCache Maven / Gradle / Ivy
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* particular file as subject to the "Classpath" exception as provided
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* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
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package nl.nn.xmldecoder.finder;
import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.util.Map;
import java.util.WeakHashMap;
/**
* A hashtable-based cache with weak keys and weak values.
* An entry in the map will be automatically removed
* when its key is no longer in the ordinary use.
* A value will be automatically removed as well
* when it is no longer in the ordinary use.
*
* @since 1.7
*
* @author Sergey A. Malenkov
*/
public final class WeakCache {
private final Map> map = new WeakHashMap>();
/**
* Returns a value to which the specified {@code key} is mapped,
* or {@code null} if this map contains no mapping for the {@code key}.
*
* @param key the key whose associated value is returned
* @return a value to which the specified {@code key} is mapped
*/
public V get(K key) {
Reference reference = this.map.get(key);
if (reference == null) {
return null;
}
V value = reference.get();
if (value == null) {
this.map.remove(key);
}
return value;
}
/**
* Associates the specified {@code value} with the specified {@code key}.
* Removes the mapping for the specified {@code key} from this cache
* if it is present and the specified {@code value} is {@code null}.
* If the cache previously contained a mapping for the {@code key},
* the old value is replaced by the specified {@code value}.
*
* @param key the key with which the specified value is associated
* @param value the value to be associated with the specified key
*/
public void put(K key, V value) {
if (value != null) {
this.map.put(key, new WeakReference(value));
}
else {
this.map.remove(key);
}
}
/**
* Removes all of the mappings from this cache.
*/
public void clear() {
this.map.clear();
}
}