/*
 * Copyright 2010 Google Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package mssql.googlecode.concurrentlinkedhashmap;

import static mssql.googlecode.concurrentlinkedhashmap.ConcurrentLinkedHashMap.checkNotNull;

import java.io.Serializable;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Set;

A common set of Weigher and EntryWeigher implementations.
Author:ben.manes@gmail.com (Ben Manes)
See Also:
/** * A common set of {@link Weigher} and {@link EntryWeigher} implementations. * * @author ben.manes@gmail.com (Ben Manes) * @see <a href="http://code.google.com/p/concurrentlinkedhashmap/"> * http://code.google.com/p/concurrentlinkedhashmap/</a> */
public final class Weighers { private Weighers() { throw new AssertionError(); }
A entry weigher backed by the specified weigher. The weight of the value determines the weight of the entry.
Params:
  • weigher – the weigher to be "wrapped" in a entry weigher.
Type parameters:
  • <K> – K
  • <V> – V
Returns:A entry weigher view of the specified weigher.
/** * A entry weigher backed by the specified weigher. The weight of the value * determines the weight of the entry. * * @param <K> K * @param <V> V * @param weigher the weigher to be "wrapped" in a entry weigher. * @return A entry weigher view of the specified weigher. */
public static <K, V> EntryWeigher<K, V> asEntryWeigher( final Weigher<? super V> weigher) { return (weigher == singleton()) ? Weighers.<K, V>entrySingleton() : new EntryWeigherView<K, V>(weigher); }
A weigher where an entry has a weight of 1. A map bounded with this weigher will evict when the number of key-value pairs exceeds the capacity.
Type parameters:
  • <K> – K
  • <V> – V
Returns:A weigher where a value takes one unit of capacity.
/** * A weigher where an entry has a weight of <code>1</code>. A map bounded with * this weigher will evict when the number of key-value pairs exceeds the * capacity. * * @param <K> K * @param <V> V * @return A weigher where a value takes one unit of capacity. */
@SuppressWarnings({"cast", "unchecked"}) public static <K, V> EntryWeigher<K, V> entrySingleton() { return (EntryWeigher<K, V>) SingletonEntryWeigher.INSTANCE; }
A weigher where a value has a weight of 1. A map bounded with this weigher will evict when the number of key-value pairs exceeds the capacity.
Type parameters:
  • <V> – V
Returns:A weigher where a value takes one unit of capacity.
/** * A weigher where a value has a weight of <code>1</code>. A map bounded with * this weigher will evict when the number of key-value pairs exceeds the * capacity. * * @param <V> V * @return A weigher where a value takes one unit of capacity. */
@SuppressWarnings({"cast", "unchecked"}) public static <V> Weigher<V> singleton() { return (Weigher<V>) SingletonWeigher.INSTANCE; }
A weigher where the value is a byte array and its weight is the number of bytes. A map bounded with this weigher will evict when the number of bytes exceeds the capacity rather than the number of key-value pairs in the map. This allows for restricting the capacity based on the memory-consumption and is primarily for usage by dedicated caching servers that hold the serialized data.

A value with a weight of 0 will be rejected by the map. If a value with this weight can occur then the caller should eagerly evaluate the value and treat it as a removal operation. Alternatively, a custom weigher may be specified on the map to assign an empty value a positive weight.

Returns:A weigher where each byte takes one unit of capacity.
/** * A weigher where the value is a byte array and its weight is the number of * bytes. A map bounded with this weigher will evict when the number of bytes * exceeds the capacity rather than the number of key-value pairs in the map. * This allows for restricting the capacity based on the memory-consumption * and is primarily for usage by dedicated caching servers that hold the * serialized data. * <p> * A value with a weight of <code>0</code> will be rejected by the map. If a value * with this weight can occur then the caller should eagerly evaluate the * value and treat it as a removal operation. Alternatively, a custom weigher * may be specified on the map to assign an empty value a positive weight. * * @return A weigher where each byte takes one unit of capacity. */
public static Weigher<byte[]> byteArray() { return ByteArrayWeigher.INSTANCE; }
A weigher where the value is a Iterable and its weight is the number of elements. This weigher only should be used when the alternative collection() weigher cannot be, as evaluation takes O(n) time. A map bounded with this weigher will evict when the total number of elements exceeds the capacity rather than the number of key-value pairs in the map.

A value with a weight of 0 will be rejected by the map. If a value with this weight can occur then the caller should eagerly evaluate the value and treat it as a removal operation. Alternatively, a custom weigher may be specified on the map to assign an empty value a positive weight.

Type parameters:
  • <E> – E
Returns:A weigher where each element takes one unit of capacity.
/** * A weigher where the value is a {@link Iterable} and its weight is the * number of elements. This weigher only should be used when the alternative * {@link #collection()} weigher cannot be, as evaluation takes O(n) time. A * map bounded with this weigher will evict when the total number of elements * exceeds the capacity rather than the number of key-value pairs in the map. * <p> * A value with a weight of <code>0</code> will be rejected by the map. If a value * with this weight can occur then the caller should eagerly evaluate the * value and treat it as a removal operation. Alternatively, a custom weigher * may be specified on the map to assign an empty value a positive weight. * * @param <E> E * @return A weigher where each element takes one unit of capacity. */
@SuppressWarnings({"cast", "unchecked"}) public static <E> Weigher<? super Iterable<E>> iterable() { return (Weigher<Iterable<E>>) (Weigher<?>) IterableWeigher.INSTANCE; }
A weigher where the value is a Collection and its weight is the number of elements. A map bounded with this weigher will evict when the total number of elements exceeds the capacity rather than the number of key-value pairs in the map.

A value with a weight of 0 will be rejected by the map. If a value with this weight can occur then the caller should eagerly evaluate the value and treat it as a removal operation. Alternatively, a custom weigher may be specified on the map to assign an empty value a positive weight.

Type parameters:
  • <E> – E
Returns:A weigher where each element takes one unit of capacity.
/** * A weigher where the value is a {@link Collection} and its weight is the * number of elements. A map bounded with this weigher will evict when the * total number of elements exceeds the capacity rather than the number of * key-value pairs in the map. * <p> * A value with a weight of <code>0</code> will be rejected by the map. If a value * with this weight can occur then the caller should eagerly evaluate the * value and treat it as a removal operation. Alternatively, a custom weigher * may be specified on the map to assign an empty value a positive weight. * * @param <E> E * @return A weigher where each element takes one unit of capacity. */
@SuppressWarnings({"cast", "unchecked"}) public static <E> Weigher<? super Collection<E>> collection() { return (Weigher<Collection<E>>) (Weigher<?>) CollectionWeigher.INSTANCE; }
A weigher where the value is a List and its weight is the number of elements. A map bounded with this weigher will evict when the total number of elements exceeds the capacity rather than the number of key-value pairs in the map.

A value with a weight of 0 will be rejected by the map. If a value with this weight can occur then the caller should eagerly evaluate the value and treat it as a removal operation. Alternatively, a custom weigher may be specified on the map to assign an empty value a positive weight.

Type parameters:
  • <E> – E
Returns:A weigher where each element takes one unit of capacity.
/** * A weigher where the value is a {@link List} and its weight is the number * of elements. A map bounded with this weigher will evict when the total * number of elements exceeds the capacity rather than the number of * key-value pairs in the map. * <p> * A value with a weight of <code>0</code> will be rejected by the map. If a value * with this weight can occur then the caller should eagerly evaluate the * value and treat it as a removal operation. Alternatively, a custom weigher * may be specified on the map to assign an empty value a positive weight. * * @param <E> E * @return A weigher where each element takes one unit of capacity. */
@SuppressWarnings({"cast", "unchecked"}) public static <E> Weigher<? super List<E>> list() { return (Weigher<List<E>>) (Weigher<?>) ListWeigher.INSTANCE; }
A weigher where the value is a Set and its weight is the number of elements. A map bounded with this weigher will evict when the total number of elements exceeds the capacity rather than the number of key-value pairs in the map.

A value with a weight of 0 will be rejected by the map. If a value with this weight can occur then the caller should eagerly evaluate the value and treat it as a removal operation. Alternatively, a custom weigher may be specified on the map to assign an empty value a positive weight.

Type parameters:
  • <E> – E
Returns:A weigher where each element takes one unit of capacity.
/** * A weigher where the value is a {@link Set} and its weight is the number * of elements. A map bounded with this weigher will evict when the total * number of elements exceeds the capacity rather than the number of * key-value pairs in the map. * <p> * A value with a weight of <code>0</code> will be rejected by the map. If a value * with this weight can occur then the caller should eagerly evaluate the * value and treat it as a removal operation. Alternatively, a custom weigher * may be specified on the map to assign an empty value a positive weight. * * @param <E> E * @return A weigher where each element takes one unit of capacity. */
@SuppressWarnings({"cast", "unchecked"}) public static <E> Weigher<? super Set<E>> set() { return (Weigher<Set<E>>) (Weigher<?>) SetWeigher.INSTANCE; }
A weigher where the value is a Map and its weight is the number of entries. A map bounded with this weigher will evict when the total number of entries across all values exceeds the capacity rather than the number of key-value pairs in the map.

A value with a weight of 0 will be rejected by the map. If a value with this weight can occur then the caller should eagerly evaluate the value and treat it as a removal operation. Alternatively, a custom weigher may be specified on the map to assign an empty value a positive weight.

Type parameters:
  • <A> – A
  • <B> – B
Returns:A weigher where each entry takes one unit of capacity.
/** * A weigher where the value is a {@link Map} and its weight is the number of * entries. A map bounded with this weigher will evict when the total number of * entries across all values exceeds the capacity rather than the number of * key-value pairs in the map. * <p> * A value with a weight of <code>0</code> will be rejected by the map. If a value * with this weight can occur then the caller should eagerly evaluate the * value and treat it as a removal operation. Alternatively, a custom weigher * may be specified on the map to assign an empty value a positive weight. * * @param <A> A * @param <B> B * @return A weigher where each entry takes one unit of capacity. */
@SuppressWarnings({"cast", "unchecked"}) public static <A, B> Weigher<? super Map<A, B>> map() { return (Weigher<Map<A, B>>) (Weigher<?>) MapWeigher.INSTANCE; } static final class EntryWeigherView<K, V> implements EntryWeigher<K, V>, Serializable { static final long serialVersionUID = 1; final Weigher<? super V> weigher; EntryWeigherView(Weigher<? super V> weigher) { checkNotNull(weigher); this.weigher = weigher; } @Override public int weightOf(K key, V value) { return weigher.weightOf(value); } } enum SingletonEntryWeigher implements EntryWeigher<Object, Object> { INSTANCE; @Override public int weightOf(Object key, Object value) { return 1; } } enum SingletonWeigher implements Weigher<Object> { INSTANCE; @Override public int weightOf(Object value) { return 1; } } enum ByteArrayWeigher implements Weigher<byte[]> { INSTANCE; @Override public int weightOf(byte[] value) { return value.length; } } enum IterableWeigher implements Weigher<Iterable<?>> { INSTANCE; @Override public int weightOf(Iterable<?> values) { if (values instanceof Collection<?>) { return ((Collection<?>) values).size(); } int size = 0; for (Object value : values) { size++; } return size; } } enum CollectionWeigher implements Weigher<Collection<?>> { INSTANCE; @Override public int weightOf(Collection<?> values) { return values.size(); } } enum ListWeigher implements Weigher<List<?>> { INSTANCE; @Override public int weightOf(List<?> values) { return values.size(); } } enum SetWeigher implements Weigher<Set<?>> { INSTANCE; @Override public int weightOf(Set<?> values) { return values.size(); } } enum MapWeigher implements Weigher<Map<?, ?>> { INSTANCE; @Override public int weightOf(Map<?, ?> values) { return values.size(); } } }