给文件的每一行后面加一个String:context

    public void readFromFile(String src_file,String des_file,String content){
        String str=null;
        try{
            FileReader f=new FileReader(src_file);
            BufferedReader ff=new BufferedReader(f);
            FileWriter f_out=new FileWriter(des_file,true);
            BufferedWriter ff_out=new BufferedWriter(f_out);
            while(ff.ready()){
                str=ff.readLine();
                ff_out.write(str+content+'\n');
            }
            ff_out.write("");//不加这个，最后一行写不完。。。
            ff.close();
            ff_out.close();
        }catch(Exception e) {
           e.printStackTrace();
        }
    }