java对同一个文件进行读写操作方法

public static void fileRevise(File file) throws IOException {
    Reader reader=new BufferedReader(new FileReader(file));
    //读取的数据用内存为中介，存取，如建立一个集合
    int len;
    char[] charArray=new char[1024];
    //集合用于储存读取的数据
    List<Character> list=new ArrayList<>();//char 类型的集合，储存char[]读取的数据
    while ((len=reader.read(charArray))!=-1){
      for (int i = 0; i <len ; i++) {
        list.add(charArray[i]);//char->string
      }
    }
    char[] newArray=new char[list.size()];
    for (int i = 0; i <list.size() ; i++) {
      newArray[i]=list.get(i);
    }
    Arrays.sort(newArray);
    Writer write=new BufferedWriter(new FileWriter(file));
    write.write(newArray);
    //关闭流
 
    reader.close();
    write.close();
  }

//用字符缓冲流的方法readline()读取，用字符串缓存，将字符串转为字符数组重新写入
  public static void fileRevise2(File file) throws IOException {
    Reader reader=new BufferedReader(new FileReader(file));
    StringBuilder sb=new StringBuilder();
    String str;
    while ((str=((BufferedReader) reader).readLine())!=null){
      sb.append(str);
    }
    System.out.print(sb);
    char[] cArray=sb.toString().toCharArray();//
    Arrays.sort(cArray);
    reader.close();
    Writer write=new BufferedWriter(new FileWriter(file));
    write.write(cArray);
    write.close();
  }