java 从数据库取数据并存入本地文本中

你从数据库获取数据的代码有问题，应该用List先获取到所有的数据，然后在遍历这个List，提前userId相同的账户问题信息。
我给你完整代码如下：你只需要修改queryData过程将ResultSet的数据存入list中返回即可。你可以先运行看结果，再修改。祝好。
代码如下：

public class WeiboDataExtract {
    public  List<WeiboData> queryData(){
        List<WeiboData> list = new ArrayList<WeiboData>();
        list.add(new WeiboData("1","hello"));
        list.add(new WeiboData("1","world"));
        list.add(new WeiboData("1","I want to change you!"));

        list.add(new WeiboData("2","Haha"));
        return list;
    }

    public void extract(List<WeiboData>datas){
        Map<String,StringBuffer> map = new HashMap<String,StringBuffer>();
        //遍历数据
        for(WeiboData data:datas){
            StringBuffer buffer = map.get(data.getUserId());
            //map中没有该微博账户，新建数据并存储
            if(buffer==null){
                buffer= new StringBuffer();
                map.put(data.getUserId(), buffer);
            }
            //将该账户的文本信息收集起来
            buffer.append(data.getText()+"\r\n");
        }

        //遍历map输出到文件
        for(Entry<String, StringBuffer> entry:map.entrySet()){
            String userId = entry.getKey();
            StringBuffer value = entry.getValue();
            writeToFile("d:/"+userId+".txt",value.toString(),true,"GB2312");
        }
    }

 
    public  void writeToFile(String fileName, String content,boolean append,String charset){
        if(fileName==null||"".equals(fileName)){
            return;
        }

        if(content==null||"".equals(content)){
            return;
        }

        //默认编码格式为UTF-8
        if(charset==null){
            charset = "UTF-8";
        }

        //将字符串写入到文件输出流中
        OutputStreamWriter osw = null;
        try {
            osw = new OutputStreamWriter(new FileOutputStream(fileName, append), charset);
            osw.write(content + "\r\n");
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally{
            if(osw!=null){
                try {
                    osw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    public static void main(String[] args) {
        WeiboDataExtract d = new WeiboDataExtract();
        d.extract(d.queryData());
    }
}

用到的一个类如下：

public class WeiboData {
    private String userId;
    private String text;

    public WeiboData(String userId, String text) {
        super();
        this.userId = userId;
        this.text = text;
    }

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }

}