英文分詞+提取詞干的修正版 
很久以前寫過一個分詞程序，也一直在用，不過之前的若干版本都有一些bug，今天趁著有空修改了一下，實現的功能包括：
1、抽取字符串中的英文單詞，如："I love you, too."可以分為i, love, you, too四個單詞
2、對于連寫的單詞也可以根據首字母大寫分詞，如：wordStemming可以分為word和stemming
3、提取詞干，仍然采用的是Snowball

import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Iterator;

import org.tartarus.snowball.SnowballProgram;

/** *//**
 * Tokenizer
 * 
 * @author Peter Cheng
 * 
 */
public class Tokenizer ...{
    /** *//**
     * Language
     */
    public static String language = "english";

    /**//* Stemmer */
    private static SnowballProgram stemmer = null;

    /**//* Stem method */
    private static Method stemMethod = null;

    /** *//**
     * Tokenize and stem
     * 
     * @param source
     *            The string to be processed
     * @return All the word stems
     */
    public static Iterator tokenize(String source) ...{
        if (Tokenizer.stemmer == null) ...{
            try ...{
                Class stemClass = Class.forName("org.tartarus.snowball.ext."
                        + Tokenizer.language + "Stemmer");
                Tokenizer.stemmer = (SnowballProgram) stemClass.newInstance();
                Tokenizer.stemMethod = stemClass
                        .getMethod("stem", new Class[0]);
            } catch (Exception e) ...{
                System.out.println("Error when initializing Stemmer!");
                System.exit(1);
            }
        }

        /**//* Tokenizer */
        ArrayList tokens = new ArrayList();
        StringBuffer buffer = new StringBuffer();
        for (int i = 0; i < source.length(); i++) ...{
            char character = source.charAt(i);
            if (Character.isLetter(character)) ...{
                buffer.append(character);
            } else ...{
                if (buffer.length() > 0) ...{
                    tokens.add(buffer.toString());
                    buffer = new StringBuffer();
                }
            }
        }
        if (buffer.length() > 0) ...{
            tokens.add(buffer.toString());
        }

        /**//* All the words */
        ArrayList words = new ArrayList();

        /**//* All the words consisting of capitals */
        ArrayList allTheCapitalWords = new ArrayList();

        /**//* Tokenize according to the capitals */
        nextToken: for (Iterator allTokens = tokens.iterator(); allTokens
                .hasNext();) ...{
            String token = (String) allTokens.next();

            /**//* The words consisting of capitals */
            boolean allUpperCase = true;
            for (int i = 0; i < token.length(); i++) ...{
                if (!Character.isUpperCase(token.charAt(i))) ...{
                    allUpperCase = false;
                }
            }
            if (allUpperCase) ...{
                allTheCapitalWords.add(token);
                continue nextToken;
            }

            /**//* Other cases */
            int index = 0;
            nextWord: while (index < token.length()) ...{
                nextCharacter: while (true) ...{
                    index++;
                    if ((index == token.length())
                            || !Character.isLowerCase(token.charAt(index))) ...{
                        break nextCharacter;
                    }
                }
                words.add(token.substring(0, index).toLowerCase());
                token = token.substring(index);
                index = 0;
                continue nextWord;
            }
        }

        /**//* Stemming */
        try ...{
            for (int i = 0; i < words.size(); i++) ...{
                Tokenizer.stemmer.setCurrent((String) words.get(i));
                Tokenizer.stemMethod.invoke(Tokenizer.stemmer, new Object[0]);
                words.set(i, Tokenizer.stemmer.getCurrent());
            }
        } catch (Exception e) ...{
            e.printStackTrace();
        }

        words.addAll(allTheCapitalWords);

        return words.iterator();
    }
}


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