hashtable问题

Question

public class CheckArtical{
    private static Hashtable W_table = new Hashtable();
    
    private static String ChangeWord(String word, String sentence){
        String chg_word = new String();
        char c;
        
        
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); 
        
        System.out.println(word);
        System.out.println(" is not in lexicon,change it!");
        
        //System.out.println(sentence+"\n");
       try{ 
        while(true){
            chg_word = br.readLine();
            //System.out.println(chg_word);
            if(chg_word.equalsIgnoreCase("Q"))System.exit(1);
            if(chg_word.equalsIgnoreCase("Quit")){
                chg_word = word;
                break;
            }
            else{
                chg_word = (String)W_table.get(chg_word);
                System.out.println(chg_word);
                if(chg_word == null)
                   
                   System.out.println("try again\n");
                else
                    break; 
                
            }
                           
        }
       }
       catch(Exception e){
           System.out.println(e);
           System.out.println("error in change word!");
           System.exit(1);
       }
        return chg_word;
    }
    
    private static void ConstructTable(){
        String word = new String();
        byte Aword[] = null;  
        ResultSet rs = null;
        Statement stm1 = null;
        Connection con1 = null;
        String JDBC_DRIVER = "com.mysql.jdbc.Driver";
        String DATABASE_URL = "jdbc:mysql://localhost/wordbase"; 
       
        
        try{
           
           Class.forName(JDBC_DRIVER);
           con1 = DriverManager.getConnection(DATABASE_URL, "root", "root");
           stm1 = con1.createStatement();
           
           //construct w_table
           rs = stm1.executeQuery("SELECT *  FROM worddatas");
           rs.beforeFirst();
           while(rs.next()){
               word = rs.getString(1);
               Aword = word.getBytes("ISO-8859-1");
               word = new String(Aword, "GB2312");
                         
               //System.out.println(Aword);
               W_table.put((String)word, (String)word);
               System.out.println((String)W_table.get((String)word));
               //i++;
               
           }
                    
           //System.out.println(i);
           // con1.close();
       }
       
       catch(Exception e){
           System.out.println(e);
           System.exit(1);
       }      } 
    
    public static void main(String[] args){
        int i, j, k;
        File in = new File(args[0]);
        File out = new File(args[1]);
        //File lex = new File(args[2]);
        //File hash = new File(args[3]);
        StringBuffer ori_sentence = new StringBuffer();
        StringBuffer chg_sentence = new StringBuffer();
        StringBuffer sentence = new StringBuffer();
        StringBuffer word = new StringBuffer();
        byte[] Aword = null;
        String GBword = new String();
        int NumberOfRead = -1;
        char Line[] = new char[8192];
        
        Locale.setDefault(Locale.SIMPLIFIED_CHINESE);
        
        //construct hashtable
        ConstructTable();
        /*
        try{
            FileReader ilex = new FileReader(lex);
            FileWriter hw = new FileWriter(hash);
            do{
                NumberOfRead = ilex.read(Line);
                for(i=0; i<NumberOfRead; i++){
                    if(Line[i] != '\n'){
                        word.append(Line[1]);
                        
                    }
                    else{
                        Aword = word.toString().getBytes("ISO-8859-1");
                        GBword = new String(Aword, "GB2312");
                        if(!GBword.equals(null))System.out.println(GBword);
                        W_table.put(GBword.intern(), GBword);
                        hw.write((String)W_table.get(GBword.intern()));
                        hw.flush();
                        word.delete(0, word.length());
                    }
                }
            }while(NumberOfRead == 8192);
           
        }
        catch(Exception e){
            System.out.println(e);
            System.exit(1);
        } */
        
        //segment and check
        ChineseSegmenter seg = ChineseSegmenter.getGBSegmenter();
        try{
            FileReader ir = new FileReader(in);
            
            FileWriter ow = new FileWriter(out);
            do{
                NumberOfRead = ir.read(Line);
                for(i=0; i<NumberOfRead; i++){
                    if((Line[i] != '。') && (Line[i] != '！') && (Line[i] != '？') && (Line[i] != '\n'))
                        sentence.append(Line[i]);
                    else{
                        ori_sentence.append(seg.segmentLine(sentence.toString(), "#"));
                       // System.out.println(ori_sentence.toString());
                        for(j=0; j<ori_sentence.length(); j++){
                            if(ori_sentence.charAt(j) != '#'){
                                word.append(ori_sentence.charAt(j));
                                System.out.println(word);
                            }
                            else{
                                //Aword = word.toString().getBytes("ISO-8859-1");
                               // GBword = new String(Aword, "GB2312");
                                GBword = (String)W_table.get(word.toString()) ;
                                if(GBword == null){
                                    //System.out.println(word);
                                    System.out.println(word.toString());
                                    chg_sentence.append(ChangeWord(word.toString(), ori_sentence.toString()));
                                    
                                }
                                else{
                                    chg_sentence.append(word.toString());
                                }
                               word.delete(0, word.length());
                            }
                            
                        }
                        ow.write(chg_sentence.toString()+Line[i]);
                        ori_sentence.delete(0, ori_sentence.length());
                        chg_sentence.delete(0, chg_sentence.length());
                        sentence.delete(0, sentence.length());
                        
                    }
                }
            }while(NumberOfRead == 8192);
        }
        catch(Exception e){
            System.out.println(e);
            System.exit(1);
        }
    }
}
我的hashtable是全局的，在函数ConstructTable中，put和get 都没有问题，可以得到正确的答案，但是在别的函数main和changeword中，总是get 不到任何值，get操作的结果得到的都是null！请高手指教，这是怎么回事？

Answer 1

我的这个程序是用来做中文分词和改词的，chinesesegmenter是一个分词程序，把一句中文根据词库分成一个个的词语。在分出的词中如果有不在词库中的则把它修改成词库中的词。

Answer 2

由于你的方法都是静态的，可能hashtable还没有生成，你就执行了
在main和changeword中
你判断一下W_table是不是为空的
if(W_table==null || W_table.size()==0){
   ConstructTable();
}

Answer 3

试过，在main中，W_table的size不是０