将文件读入数组列表，但参数列表的长度不同

Question

我被困在一个文件IO的问题上。基本上，有一个名为“学生”的类，还有一个名为“读取学生”的方法，它将返回一个 ArrayList 对象。

我被要求读取一个文件，并通过单个空格将它们分成3个部分，并且不允许使用扫描仪。

文件：

艾米·摩尔 60

克洛伊·斯科特 40

我的问题是，（1）由于学生类只有两个参数（字符串，双精度），我如何将两个字符串和一个双精度添加到学生中？（2）学生班级提供的没有toString（）方法，我该如何打印出来？

如果有人能帮助我，我将不胜感激。

学生的构造函数是这样的：

 public Student(String sstudent, double mmark) 

已读学生：

 public static ArrayList<Student> readStudent(String fName){

到目前为止，我做了什么：

 ArrayList<Student> list=new ArrayList<Student>();

 try{

    BufferedReader br=new BufferedReader(new FileReader(fName));

     String line;

     while((line=br.readLine())!=null){

        String[] splitLine=line.split(" ");

        String first=splitLine[0];

        String second=splitLine[1];

        Double third=Double.parseDouble(splitLine[3]);

       Student stu=

            new Student(first,second));

        list.add(stu);

    }

  ...... 

  return list;

}

Answer 1

对于您的问题 （1）Student s = new Student(first + " " + second, third);//by the way for third,it is not splitLine[3],it is splitLine[2]对于您的问题 （2）ArrayList<Student> studentList = readStudent("YourFileName");for(Student s : studentList)&nbsp; &nbsp; System.out.println(s.name + " " + s.grade);//don't know what are the variable names of Student class instances

Answer 2

您在代码中有不同的选择：//问题1（请参阅上面的第一条评论）：如果您出于任何原因不需要第一，第二和第三，请选择选项1（这是有效的）。public static ArrayList<Student> readStudent(String fName) throws FileNotFoundException, IOException{&nbsp; &nbsp; &nbsp; &nbsp; ArrayList<Student> list=new ArrayList<Student>();&nbsp; &nbsp; &nbsp; &nbsp; //try{&nbsp; &nbsp; &nbsp; &nbsp; BufferedReader br=new BufferedReader(new FileReader(fName));&nbsp; &nbsp; &nbsp; &nbsp; String line;&nbsp; &nbsp; &nbsp; &nbsp; while((line=br.readLine())!=null){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; //option1&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; String[] splitLine=line.split(" ");&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Student stu = new Student(splitLine[0] + " " + splitLine[1], splitLine[2]);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; //option2//&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; String first=splitLine[0];//&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; String second=splitLine[1];//&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; double third=Double.parseDouble(splitLine[3]);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;//&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Student stu = new Student(first + " " + second, third);&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; list.add(stu);&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; //......&nbsp; &nbsp; &nbsp; &nbsp; return list;&nbsp; &nbsp; }问题 2：在 Java 中，获取器和设置器用于访问类的属性（它是首选样式）。检查是否有一些在课堂上的学生，然后使用它。在选项 2 中，您可以访问学生对象的方向全局变量。printStudents(readStudent("your file name"));&nbsp; &nbsp; &nbsp;//print a list of student objects&nbsp;void printStudents(List<Student> students){&nbsp; &nbsp; for(Student stu: students)&nbsp; &nbsp; &nbsp; &nbsp; //option 1: using getter&nbsp; &nbsp; &nbsp; &nbsp; System.out.println(stu.getSStudent()+"&nbsp; "+stu.getMark());&nbsp; &nbsp; &nbsp; &nbsp; //option 2: accessing attributes&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; //System.out.println(stu.sstudent+"&nbsp; "+stu.mark);}