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The S-Space Package is a collection of algorithms for building Semantic Spaces as well as a highly-scalable library for designing new distributional semantics algorithms. Distributional algorithms process text corpora and represent the semantic for words as high dimensional feature vectors. This package also includes matrices, vectors, and numerous clustering algorithms. These approaches are known by many names, such as word spaces, semantic spaces, or distributed semantics and rest upon the Distributional Hypothesis: words that appear in similar contexts have similar meanings.

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/*
 * Copyright 2009 David Jurgens
 *
 * This file is part of the S-Space package and is covered under the terms and
 * conditions therein.
 *
 * The S-Space package is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation and distributed hereunder to you.
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND NO REPRESENTATIONS OR WARRANTIES,
 * EXPRESS OR IMPLIED ARE MADE.  BY WAY OF EXAMPLE, BUT NOT LIMITATION, WE MAKE
 * NO REPRESENTATIONS OR WARRANTIES OF MERCHANT- ABILITY OR FITNESS FOR ANY
 * PARTICULAR PURPOSE OR THAT THE USE OF THE LICENSED SOFTWARE OR DOCUMENTATION
 * WILL NOT INFRINGE ANY THIRD PARTY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER
 * RIGHTS.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see .
 */

package edu.ucla.sspace.util;

import java.util.LinkedHashMap;
import java.util.Map;


/**
 * A special-purpose {@link Map} that acts as an LRU cache for a fixed number of
 * elements.  Classes may use this to retain a limited nubmer of frequently-used
 * mappings.  For more details see {@link LinkedHashMap} on its access-order.
 *
 * @see LinkedHashMap
 */
public class BoundedCache extends LinkedHashMap {

    private static final long serialVersionUID = 1L;
    
    /**
     * The maximum number of elements to retain in the map
     */
    private final int maxSize;

    /**
     * Creates a cache that retains at most {@code maxSize} elements
     */
    public BoundedCache(int maxSize) {
        super(maxSize, .75f, true);
        this.maxSize = maxSize;
    }
    
    /**
     * Returns {@code true} if the addition of some entry has caused the current
     * size of the map to exceed its maximum size.
     */
    protected boolean removeEldestEntry(Map.Entry eldest) {
        return size() > maxSize;
    }
}