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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.text;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

import java.util.Iterator;
import java.util.Queue;

import java.util.concurrent.ConcurrentLinkedQueue;

/**
 * An iterator implementation that returns {@link Document} instances given a
 * file that contains list of files.
 *
 * 
 *
 * This class is thread-safe.
 */
public class FileListDocumentIterator implements Iterator {

    /**
     * The files in the list that have yet to be returned as {@code Document}
     * instances
     */
    private final Queue filesToProcess;
    
    /**
     * Creates an {@code Iterator} over the files listed in the provided file.
     *
     * @code fileListName a file containing a list of file names with one per
     *       line
     *
     * @throws IOException if any error occurs when reading {@code fileListName}
     */
    public FileListDocumentIterator(String fileListName) throws IOException {
	
	filesToProcess = new ConcurrentLinkedQueue();
	
	// read in all the files we have to process
	BufferedReader br = new BufferedReader(new FileReader(fileListName));
	for (String line = null; (line = br.readLine()) != null; )
	    filesToProcess.offer(line.trim());	    

	br.close();
    }

    /**
     * Returns {@code true} if there are more documents to return.
     */
    public boolean hasNext() {
	return !filesToProcess.isEmpty();
    }
    
    /**
     * Returns the next document from the list.
     */
    public Document next() {
	String fileName = filesToProcess.poll();
	if (fileName == null) 
	    return null;
	try {
	    return new FileDocument(fileName);
	} catch (IOException ioe) {
	    return null;
	}
    }	
    
    /**
     * Throws an {@link UnsupportedOperationException} if called.
     */
    public void remove() {
	throw new UnsupportedOperationException(
	    "removing documents is not supported");
    }
}