如何写文件

public class WordWriter{


public static void main(String[] args) throws IOException {
     WordWriter lw=new WordWriter("a.txt");
     lw.append("学习");
}
    /**
     * filename of the log file
     */
    protected String filename;
    /**
     * the log file
     */
    protected File file;
    /**
     * the file writer
     */
    protected FileWriter fWriter;
    /**
     * the print writer (we can invoke function : println(String))
     */
    protected PrintWriter pWriter;

    /**
     * Constructor
     *
     * @param        filename        the filename of the log
     *
     */
    public WordWriter(String filename) throws IOException{
        this.filename = filename;
        file = new File(filename);
    }

    /**
     * append a new line to the log file, also output it to console
     *
     * @param      log          the string to write to file
     *
     */
    public synchronized void append(String log){
        fWriter = null;
        pWriter = null;
        try{
            fWriter = new FileWriter(file, true);
            pWriter = new PrintWriter(fWriter);
            // append to log file
            pWriter.println(log);
            // output it to console
            System.out.println(log);
        }catch (IOException e){
            System.out.println ("Error Writing log file: " + e);
        }finally{
            try{
                if (pWriter != null){
                    pWriter.close();
                }
                if (fWriter != null){
                    fWriter.close();
                }
            }catch (IOException e){}
        }
    }

    /**
     * Return the length of the log file
     *
     * @return       the length of the log file
     *
     */
    public long getLength(){
        return file.length();
    }

    /**
     * append a new line to the log file, also output it to console
     *
     * @param      obj          the object to write to file
     *
     */
    public void append(Object obj) throws IOException{
        append(obj.toString());
    }

}