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https://github.com/haraldk/TwelveMonkeys.git
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Moving files around
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Erlend Hamnaberg
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/*
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* Copyright (c) 2008, Harald Kuhr
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name "TwelveMonkeys" nor the
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* names of its contributors may be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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package com.twelvemonkeys.util;
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import java.util.Map;
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import java.util.LinkedHashMap;
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import java.util.Iterator;
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/**
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* Map implementation with size limit, that keeps its entries in LRU
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* (least recently used) order, also known as <em>access-order</em>.
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* When the size limit is reached, the least recently accessed mappings are
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* removed. The number of mappings to be removed from the map, is
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* controlled by the trim factor.
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* <p>
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* <ul>
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* <li>Default size limit is 1000 elements.
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* See {@link #setMaxSize(int)}/{@link #getMaxSize()}.</li>
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* <li>Default trim factor is 1% ({@code 0.01f}).
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* See {@link #setTrimFactor(float)}/{@link #getTrimFactor()}.</li>
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* </ul>
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*
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* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
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* @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/util/LRUHashMap.java#1 $
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*/
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public class LRUHashMap<K, V> extends LinkedHashMap<K, V> implements ExpiringMap<K, V> {
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private int mMaxSize = 1000;
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private float mTrimFactor = 0.01f;
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/**
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* Creates an LRUHashMap with default max size (1000 entries).
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*
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* <small>This is constructor is here to comply with the reccomendations for
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* "standard" constructors in the {@code Map} interface.</small>
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*
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* @see #LRUHashMap(int)
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*/
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public LRUHashMap() {
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super(16, .75f, true);
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}
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/**
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* Creates an LRUHashMap with the given max size.
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*
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* @param pMaxSize size limit
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*/
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public LRUHashMap(int pMaxSize) {
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super(16, .75f, true);
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setMaxSize(pMaxSize);
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}
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/**
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* Creates an LRUHashMap with initial mappings from the given map,
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* and default max size (1000 entries).
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*
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* <small>This is constructor is here to comply with the reccomendations for
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* "standard" constructors in the {@code Map} interface.</small>
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*
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* @param pContents the map whose mappings are to be placed in this map.
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* May be {@code null}.
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*
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* @see #LRUHashMap(java.util.Map, int)
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*/
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public LRUHashMap(Map<? extends K, ? extends V> pContents) {
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super(16, .75f, true);
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putAll(pContents);
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}
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/**
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* Creates an LRUHashMap with initial mappings from the given map,
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* and the given max size.
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*
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* @param pContents the map whose mappings are to be placed in this map.
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* May be {@code null}.
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* @param pMaxSize size limit
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*/
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public LRUHashMap(Map<? extends K, ? extends V> pContents, int pMaxSize) {
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super(16, .75f, true);
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setMaxSize(pMaxSize);
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putAll(pContents);
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}
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/**
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* Returns the maximum number of mappings in this map.
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*
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* @return the size limit
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*/
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public int getMaxSize() {
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return mMaxSize;
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}
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/**
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* Sets the maximum number of elements in this map.
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*
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* If the current size is greater than the new max size, the map will be
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* trimmed to fit the new max size constraint.
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*
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* @see #removeLRU()
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*
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* @param pMaxSize new size limit
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*/
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public void setMaxSize(int pMaxSize) {
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if (pMaxSize < 0) {
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throw new IllegalArgumentException("max size must be positive");
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}
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mMaxSize = pMaxSize;
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while(size() > mMaxSize) {
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removeLRU();
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}
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}
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/**
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* Returns the current trim factor.
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* <p>
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* The trim factor controls how many percent of the maps current size is
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* reclaimed, when performing an {@code removeLRU} operation.
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* Defaults to 1% ({@code 0.01f}).
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*
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* @return the current trim factor
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*/
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public float getTrimFactor() {
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return mTrimFactor;
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}
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/**
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* Sets the trim factor.
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* <p>
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* The trim factor controls how many percent of the maps current size is
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* reclaimed, when performing an {@code removeLRU} operation.
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* Defaults to 1% ({@code 0.01f}).
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*
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* @param pTrimFactor the new trim factor. Acceptable values are between
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* 0 (inclusive) and 1 (exclusive).
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*
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* @see #removeLRU()
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*/
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public void setTrimFactor(float pTrimFactor) {
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if (pTrimFactor < 0f || pTrimFactor >= 1f) {
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throw new IllegalArgumentException("trim factor must be between 0 and 1");
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}
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mTrimFactor = pTrimFactor;
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}
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/**
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* always returns {@code false}, and instead invokes {@code removeLRU()}
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* if {@code size >= maxSize}.
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*/
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protected boolean removeEldestEntry(Map.Entry<K, V> pEldest) {
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// NOTE: As removeLRU() may remove more than one entry, this is better
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// than simply removing the eldest entry.
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if (size() >= mMaxSize) {
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removeLRU();
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}
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return false;
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}
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/**
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* Default implementation does nothing.
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* May be used by clients as a call-back to notify when mappings expire from
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* the map.
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*
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* @param pRemoved the removed mapping
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*/
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public void processRemoved(Map.Entry<K, V> pRemoved) {
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}
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/**
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* Removes the least recently used mapping(s) from this map.
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* <p>
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* How many mappings are removed from the map, is controlled by the
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* trim factor.
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* In any case, at least one mapping will be removed.
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*
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* @see #getTrimFactor()
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*/
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public void removeLRU() {
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int removeCount = (int) Math.max((size() * mTrimFactor), 1);
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Iterator<Map.Entry<K, V>> entries = entrySet().iterator();
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while ((removeCount--) > 0 && entries.hasNext()) {
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entries.next();
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entries.remove();
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}
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}
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}
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