有勇气的牛排
官方地址: ​​​https://www.couragesteak.com/​​

按行读取

public static void readFile(){
  String pathname = "E:/project/java/idea项目/java学习/test.txt";
  String line;
  try{
    FileReader reader = new FileReader(pathname);
    BufferedReader br = new BufferedReader(reader);
  while ((line=br.readLine())!=null){
    System.out.println(line);
  }
  
  } catch (IOException e){
    e.printStackTrace();
  }
}

写入文件

public static void writeFile(){
  try{
    String pathname = "E:/project/java/idea项目/java学习/test.txt";
    File writeName = new File(pathname);
    
    FileWriter writer = new FileWriter(writeName);
    BufferedWriter out = new BufferedWriter(writer);
    out.write("666");
    out.write("1\r2\n3");
        out.flush(); // 把缓存区内容压入文件
    
  } catch (IOException e){
    e.printStackTrace();
  }
}

文件内容：