Question

我正在尝试分离一组数据。我需要将每个数据存储到一个变量中，然后创建一个对象并将它们放在一个ArrayList中。

数据集采用此格式

lastName, firstName
ID num_courses
course1_name 
grade units
course2_name
grade units
....

到目前为止，我已经完成了这项工作，但我在创建多个对象，存储数据以及将其添加到ArrayList []时遇到了问题。感谢您的时间和帮助（：

public static void main (String[] args) throws FileNotFoundException {
Scanner scnr = new Scanner(System.in);
System.out.println("Enter file name: ");
String fileName = scnr.nextLine();
Scanner inFile = new Scanner(new FileInputStream(fileName)); //importing filename

ArrayList<String> list = new ArrayList<String>(); //for list of courses
String name = "";
String id = "";
int coursesTaken = 0;
String courseName = "";
char grade;
int courseUnit = 0;

while(inFile.hasNextLine()){
    name = inFile.nextLine(); //first line is name
    StringTokenizer st = new StringTokenizer(inFile.nextLine()); //separting whitespace
    id = st.nextToken(); //storing ID
    coursesTaken = Integer.parseInt(st.nextToken()); //storing num_courses_taken

    Student s1 = new Student(name, id); //FIXME (need more than 1 student object)

    for(int i = 0; i < coursesTaken*2; ++i){
        courseName = inFile.nextLine();
        s1.addCourses(courseName); //adding to arrayList

        StringTokenizer st2 = new StringTokenizer(inFile.nextLine());
        grade = st2.nextToken().charAt(0);
        courseUnit = Integer.parseInt(st2.nextToken());

        Course ci = new Course(courseName, grade, courseUnit); //FIXME (need more than 1 course)


        }

    }
}

Course.java

public class Course {
    private String name;
    private char grade;
    private int units;


    //constructors
    public Course(){
        name = "";
        grade = 0;
        units = 0;
    }

    public Course(String name, char grade, int units){
        this.name = name;
        this.grade = grade;
        this.units = units;
    }

    //getters 
    public String getName(){
        return name;
    }

    public char getGrade(){
        return grade;
    }

    public int getUnits(){
        return units;
    }

    //setters
    public void setName(String name){
        this.name = name;
    }

    public void setGrade(char grade){
        this.grade = grade;
    }

    public void setUnits(int units){
        this.units = units;
    }  
}

Student.java

public class Student {

    private String name;
    private String id;
    private ArrayList<String> listCourses = new ArrayList<String>();

    //constructor
    //default
    public Student(){
        name = "none";
        id = "none";
        //courses = "none";
    }

    public Student(String name, String id){
        this.name = name;
        this.id = id;
        //this.courses = courses;
    }


    //getters
    public String getName(){
        return name;
    }

    public String getId(){
        return id;
    }

    public ArrayList<String> getCourses(){
        return listCourses;
    }


    //setters
    public void setName(String name){
        this.name = name;
    }

    public void setId (String id){
        this.id = id;
    }

    public void addCourses(String courses){
        listCourses.add(courses);
    }
}

Answer 1

//用于课程列表

这是一个字符串列表。

这是一个课程列表

List<Course> list = new ArrayList<>();

然后，只在循环中list.add(ci)

旁注：Student.addCourses应该是单数，并且可能接受Course对象

Answer 2

首先，您需要一个列表来存储您的学生：

18/01/30 03:35:45 INFO tool.ImportTool: Destination directory wasb://sample@workingclusterblob.blob.core.windows.net/source/employ is not present, hence not deleting.
18/01/30 03:35:45 INFO mapreduce.ImportJobBase: Beginning query import.
18/01/30 03:35:46 INFO client.AHSProxy: Connecting to Application History server at headnodehost/10.0.0.19:10200
18/01/30 03:35:46 ERROR tool.ImportTool: Encountered IOException running import job: org.apache.hadoop.mapred.FileAlreadyExistsException: Output directory wasb://sample@workingclusterblob.blob.core.windows.net/source/employ already exists

在解析所有字段时，您应该将每个创建的学生添加到此列表中：

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

其次，我认为，最好将students.add(s1);字段从listCourses更改为ArrayList<String> - 以存储有关ArrayList<Course>对象内所有学生课程的信息。

第三，您不需要将Student乘以2，因为您为每门课程致电coursesTaken 两次。

inFile.nextLine()

最后你的主要方法如下：

for (int i = 0; i < coursesTaken; i++)

更新：学生班级的变化：

private ArrayList<Course> listCourses = new ArrayList<>();

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

while(inFile.hasNextLine()){
    name = inFile.nextLine(); //first line is name
    StringTokenizer st = new StringTokenizer(inFile.nextLine()); //separting whitespace
    id = st.nextToken(); //storing ID
    coursesTaken = Integer.parseInt(st.nextToken()); //storing num_courses_taken

    Student s1 = new Student(name, id);
    ArrayList<Course> courses = new ArrayList<>();

    for(int i = 0; i < coursesTaken; i++){
        courseName = inFile.nextLine();

        StringTokenizer st2 = new StringTokenizer(inFile.nextLine());
        grade = st2.nextToken().charAt(0);
        courseUnit = Integer.parseInt(st2.nextToken());

        courses.add(new Course(courseName, grade, courseUnit)); //FIXED

    }
    s1.setListCourses(courses);
    students.add(s1); //FIXED

}

在ArrayList中分离数据和存储？

2 个答案: