往项目中一个文件中写入数据进行数据备份或者日志记录

//读数据

private static void readFileToLocal(){
    File file = new File("D:/logs/testlog.txt");
    StringBuilder result = new StringBuilder();
    try {
        BufferedReader reader = new BufferedReader(new FileReader(file));
        String s = null;
        while((s=reader.readLine())!=null){
            result.append(System.lineSeparator()+s);
        }
        reader.close();
    }catch (Exception e){
        e.printStackTrace();
    }
    System.out.println(result.toString());
}

//写数据

private static void writeDataToFile(){
    FileWriter fileWriter = null;
    File file = new File("D:/logs/testlog.txt");
    try {
        if(!file.exists()){
            file.createNewFile();
        }
        fileWriter = new FileWriter(file);
        for(int i=0;i<5;i++){
            fileWriter.write("我就是测试一下啦啦啦,num="+i+",\r\n");
            fileWriter.flush();
        }
        System.out.println("写数据成功啦!!!");
    }catch (Exception e){
        e.printStackTrace();
    }finally {
        if(fileWriter != null){
            try {
                fileWriter.close();
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    }
}