src/org/nutz/lang/stream/StringOutputStream.java
@Override
    public void flush() throws IOException {
        if (null != baos) {
            baos.flush();
            if (baos.size() > 0) {
                if (charset == null)
                    sb.append(new String(baos.toByteArray()));
                else
                    sb.append(new String(baos.toByteArray(), charset));
                baos.reset();
            }
        }
    }
@Override
    public void flush() throws IOException {
        if (null != baos) {
            baos.flush();
            if (baos.size() > 0) {
                if (charset == null)
                    sb.append(new String(baos.toByteArray()));
                else
                    sb.append(new String(baos.toByteArray(), charset));
                baos.reset();
            }
        }
    }
使用StringBuilder前,务必调用