获得文本文件编码格式

   private String initBookEncode(FileInputStream fileInputStream) {        String encode = "gb2312";    try{            byte[] head = new byte[3];              fileInputStream.read(head);            if(head[0]==-17 && head[1]==-69 && head[2] ==-65)              encode = "UTF-8";            else if (head[0] == -1 && head[1] == -2 )              encode = "UTF-16";              else if (head[0] == -2 && head[1] == -1 )              encode = "Unicode";     }catch (IOException e) {            Log.e(Global.TAG, "can't get book encoding:"+e.getMessage());}    return encode;    }