从文件中返回数组列表

Question

方法获取文件名，我需要返回一个ArrayList<<ArrayList<String>>，其中每一行都转换为ArrayList<String>，每个字符串都是该行中的一个单词。

我的txt文件是这个

Twinkle twinkle little star
How I wonder what you are
Up above the world so high
Like a diamond in the sky

所以它应该返回一个大小为 4 的数组列表，其元素是大小为 4 的字符串的数组列表，第二个元素是大小为 6 的字符串的数组列表，依此类推

但是我不确定如何将行变成单个字符串，这就是我目前所拥有的

public static ArrayList<ArrayList<String>> file (String fname){
  ArrayList<ArrayList<String>> w1 = new ArrayList<ArrayList<String>>();
  ArrayList<String> w2 = new ArrayList<String>();
  try{ 
    BufferedReader br = new BufferedReader (new FileReader(fname));
    String line= "";    

    while ((line = br.readLine()) != null){
        w2.add(line);
        w1.add(w2);
    }

  }catch(IOException e){
      System.out.println("An error occured");
  } 
  return w1;
}

Answer 1

public static ArrayList<ArrayList<String>> file (String fname){
      ArrayList<ArrayList<String>> w1 = new ArrayList<ArrayList<String>>();
      ArrayList<String> w2 = new ArrayList<String>();
      try{ 
        BufferedReader br = new BufferedReader (new FileReader(fname));
        String line= "";    

        while ((line = br.readLine()) != null){
            //take each line and split them around a space
            String[] individualWords = line.split("\\s+");
            //now convert the string[] to an arraylist
            w2 = new ArrayList<>(Arrays.asList(individualWords));
            //now add it to your main arraylist of arraylist strings
            w1.add(w2);
        }

      }catch(IOException e){
          System.out.println("An error occured");
      } 
      return w1;
    }

Answer 2

也许只是

public static ArrayList<ArrayList<String>> file (String fname){
    return Files.lines(Paths.get(fname))
                .map(line -> line.split("\\s+"))
                .map(words -> Arrays.stream(words).collect(Collectors.toList()))
                .collect(Collectors.toList());
}