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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.Comparator;
import java.util.Map;
import java.util.TreeMap;

/**
 * A {@code Map} implementation that grows to a fixed size and then retains only
 * a fixed number of the highest (largest) keys.  All keys used in this class
 * must implements {@link Comparable}.
 *
 * @see BoundedSortedMultiMap
 */
public class BoundedSortedMap extends TreeMap {

    private static final long serialVersionUID = 1;

    /**
     * The maximum number of mappings to retain.
     */
    private final int bound;
    
    /**
     * Creatins an instance that will only retain the specified number of the
     * largest (highest) keys.
     *
     * @param bound the number of mappings to retain
     */
    public BoundedSortedMap(int bound) {
        this(bound, null);
    }

    /**
     * Creatins an instance that will only retain the specified number of keys,
     * where the keys are orded according to the given {@link Comparator}.
     *
     * @param bound the number of mappings to retain
     * @param comparator The {@link Comparator} used to compare two keys
     */
    public BoundedSortedMap(int bound, Comparator comparator) {
        super(comparator);
        this.bound = bound;
    }

    /**
     * Adds the key-value mapping to this map, and if the total number of
     * mappings exceeds the bounds, removes either the currently lowest element,
     * or if reversed, the currently highest element.
     *
     * @param key {@inheritDoc}
     * @param value {@inheritDoc}
     */
    public V put(K key, V value) {
        V old = super.put(key, value);
        if (size() > bound) {
            remove(firstKey());
        }
        return old;
    }

    /**
     * Adds all of the key-value mapping to this map, and if the total number of
     * mappings exceeds the bounds, removes mappings until the size is within
     * bounds.
     *
     * @param m {@inheritDoc}
     */
    public void putAll(Map m) {
        for (Map.Entry e : m.entrySet())
            put(e.getKey(), e.getValue());
    }
}