java - 我应该如何用Java解析这个？

Question

我无法理解如何解析具有未知数量“学生”的文本文档。我的所有解决方案都很奇怪，而且我在使用扫描仪时遇到了问题。分解输入，第一个整数代表有多少个类(class)，第一个字符串是类(class)名称，下面是学生的相应日期和需要与学生一起存储的变量，学生数量未知。我想存储每个学生以及他们所在的类(class)。

到目前为止，我的代码非常困惑和困惑:

    String filename = "input.txt";
    File file = new File(filename);
    Scanner sc = new Scanner(file);
    Student[] studArr = new Student[100];
    int studCounter = 0;
    boolean breaker = false;
    boolean firstRun = true;
    int numClasses = sc.nextInt();
    System.out.println(numClasses);


    while(sc.hasNextLine()){
        String className = sc.nextLine();
        System.out.println("Name: " + className);
        String test = null;
        breaker = false;
        sc.nextLine();

        // Breaks the while loop when a new class is found
        while (breaker == false){
            Student temp = null;

            // Boolean to tell when the first run of the loop
            if (firstRun == true){
                temp.name = sc.nextLine();
            }

            else
                temp.name = test;

            System.out.println(temp.name);

            temp.date = sc.nextLine();

            if (temp.date.isEmpty()){
                System.out.println("shit is empty yo");
            }

            temp.timeSpent = sc.nextInt();
            temp.videosWatched = sc.nextInt();
            temp.className = className;
            studArr[studCounter] = temp;
            studCounter++;
            sc.nextLine();
            test = sc.nextLine();
            firstRun = false;
        }
    }
}
}

class Student {
    public String name;
    public String date;
    public String className;
    public int timeSpent;
    public int videosWatched;
}

我不需要确切的答案，但我应该寻找与扫描仪不同的工具吗？有什么方法可以研究吗？

感谢您的帮助。

Answer 1

我想出了以下解决方案。扫描仪是完成这项工作的好工具。棘手的部分是，您必须提前查看是否有空行或日期，才能知道是否有学生或类(class)。

import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Scanner;

public class Parser {

  private static String nextLine(Scanner sc) {
    String line;
    while (sc.hasNext()) {
      if (!(line = sc.nextLine()).isEmpty()) {
        return line;
      }
    }
    return null;
  }

  public static ArrayList<Student>[] parseFile(String fileName) {
    File file = new File(fileName);
    try (Scanner sc = new Scanner(file)) {
      int numClasses = sc.nextInt();
      String className = nextLine(sc);
      ArrayList<Student>[] classList = new ArrayList[numClasses];
      for (int i = 0; i < numClasses; i++) {
        classList[i] = new ArrayList<>();
        while (true) {
          String studentOrClassName = nextLine(sc);
          if (studentOrClassName == null) {
            break;
          }
          String dateOrBlankLine = sc.nextLine();
          if (dateOrBlankLine.isEmpty()) {
            className = studentOrClassName;
            break;
          }
          int timeSpent = sc.nextInt(); 
          int videosWatched = sc.nextInt();
          classList[i].add(new Student(className, dateOrBlankLine, studentOrClassName, timeSpent, 
              videosWatched));
        }
      }
      return classList;
    } catch (FileNotFoundException e) {
      e.printStackTrace();
    }
    return new ArrayList[0];
  }

  public static void main(String[] args) {
    for (ArrayList<Student> students : parseFile("classList.txt")) {
      if (!students.isEmpty()) {
        System.out.println(students.get(0).className);
      }
      for (Student student : students) {
        System.out.println(student);
      }
    }
  }

  static class Student {

    public String className;
    public String date;
    public String name;
    public int timeSpent;
    public int videosWatched;


    public Student(String className, String date, String name, int timeSpent,
        int videosWatched) {
      this.className = className;
      this.date = date;
      this.name = name;
      this.timeSpent = timeSpent;
      this.videosWatched = videosWatched;
    }

    public String toString() {
      return name + '\n' + date + '\n' + timeSpent + '\n' + videosWatched + '\n';
    }
  }
}