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The S-Space Package is a Natural Language Processing library for distributional semantics representations. Distributional semantics representations model the meaning of words, phrases, and sentences as high dimensional vectors or probability distributions. The library includes common algorithms such as Latent Semantic Analysis, Random Indexing, and Latent Dirichlet Allocation. The S-Space package also includes software libraries for matrices, vectors, graphs, and numerous clustering algorithms.

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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.AbstractSet;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;


/**
 * A space-efficient set of {@link String} instances.  In addition to providing
 * reduced space usage, testing for contains may offer increased performance
 * over a {@link java.util.HashMap} of String instances due to not requiring the
 * {@link String#hashCode()} to be computed.
 *
 * 

 *
 * This class is not synchronized.  If concurrent updating behavior is required,
 * the map should be wrapped using {@link
 * java.util.Collections#synchronizedSet(Set)}.  This map will never throw a
 * {@link java.util.ConcurrentModificationException} during iteration.  The
 * behavior is unspecified if the map is modified while an iterator is being
 * used.
 *
 * @author David Jurgens
 */
public class TrieSet extends AbstractSet {
    
    /**
     * The map that contains this sets value
     */
    private final TrieMap backingMap;

    /**
     * Creates an empty set of strings.
     */
    public TrieSet() {
        backingMap = new TrieMap();
    }

    /**
     * Creates a set of the strings contained in the collection.
     */
    public TrieSet(Collection c) {
        this();
        for (String s : c)
            backingMap.put(s, Boolean.valueOf(true));
    }

    /**
     * Adds the specified element to this set if it is not already present.
     */
    public boolean add(String s) {
        return backingMap.put(s, Boolean.valueOf(true)) == null;
    }

    /**
     * Removes all of the elements from this set.
     */
    public void clear() {
        backingMap.clear();
    }
    
    /**
     * Returns {@code true} if this set contains the specified element.
     */
    public boolean contains(Object o) {
        return backingMap.containsKey(o);
    }

    /**
     * Returns {@code true} if this set contains no elements.
     */
    public boolean isEmpty() {
        return backingMap.isEmpty();
    }

    /**
     * Returns an iterator over the elements in this set.
     */
    public Iterator iterator() {
        return backingMap.keySet().iterator();
    }

    /**
     * Removes the specified element from this set if it is present.
     */
    public boolean remove(Object o) {
        return backingMap.remove(o) != null;
    }
    
    /**
     * Returns the number of elements in this set.
     */
    public int size() {
        return backingMap.size();
    }

    public String toString() {
        return backingMap.keySet().toString();
    }
}
    

    

    

            

    

            



    
    






    
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