怎么通过代码修改properties文件？

        File file = new File("D://param.properties");         FileInputStream fis = null;        FileOutputStream fos = null;        try {            fis = new FileInputStream(file);            Properties prop = new Properties();            prop.load(fis);            prop.setProperty("key", "3");            fos = new FileOutputStream(file);            prop.store(fos, null);        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }finally{            try {                fis.close();                fos.close();            } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }                    }