java - 需要 txt 文件中的数据(以逗号分隔)，以使用现有类中的对象填充数组列表

Question

我需要:

• 从文本文件中获取输入并逐行读取，
• 获取每一行并将其拆分为学生对象并将这些值发送到数组列表，
• 将对象的数组列表从 Student 类发送到我的 servlet，
• 将 servlet 中的数组列表发送到我的 jsp 页面
• 在 html 表格中显示值。

这是我针对此特定功能的页面。我在这个项目中涉及许多不同的 java 页面、servlet 和 jsp 页面，因此如果您需要其中的任何内容，请直接询问。

文本文件包含按以下顺序排列的学生信息:

Student ID, Last Name, First Name, Quiz Scores 1-5, Makeup Quiz Score, Midterm Score, Problems Score, and Final Exam Score.

文本文件的格式示例如下:

1234,Some,Person,98.0,94.0,97.0,96.0,99.0,0.0,92.0,95.0,99.0 1235,Another,Person,89.0,99.0,87.0,85.0,88.0,0.0,89.0,98.0,99.0 1236,Onemore,Person,89.0,98.0,89.0,98.0,97.0,0.0,79.0,89.0,99.0

但是，我在表格中得到的输出只是第一行，并且全部位于第一个单元格中。

如果你能给我指出正确的方向，我就完全迷失了。

这是我的学生类(class)页面:

public class Student {
private String sid,fnm,lnm,lgrade;
private double q1,q2,q3,q4,q5,qmkup,midt,probs,finex,qavg,cavg;

public Student (){
    //empty constructor
    sid="";
    lnm="";
    fnm="";
    lgrade="";
    q1= 0;
    q2= 0;
    q3= 0;
    q4= 0;
    q5= 0;
    qmkup= 0;
    midt= 0;
    probs= 0;
    finex= 0;
    qavg= 0;
    cavg= 0;
}



public String getSid() {
    return sid;
}

public void setSid(String sid) {
    this.sid = sid;
}

public String getFnm() {
    return fnm;
}

public void setFnm(String fnm) {
    this.fnm = fnm;
}

public String getLnm() {
    return lnm;
}

public void setLnm(String lnm) {
    this.lnm = lnm;
}

public String getLgrade() {
    return lgrade;
}

public double getQ1() {
    return q1;
}

public void setQ1(double q1) {
    this.q1 = q1;
}

public double getQ2() {
    return q2;
}

public void setQ2(double q2) {
    this.q2 = q2;
}

public double getQ3() {
    return q3;
}

public void setQ3(double q3) {
    this.q3 = q3;
}

public double getQ4() {
    return q4;
}

public void setQ4(double q4) {
    this.q4 = q4;
}

public double getQ5() {
    return q5;
}

public void setQ5(double q5) {
    this.q5 = q5;
}

public double getQmkup() {
    return qmkup;
}

public void setQmkup(double qmkup) {
    this.qmkup = qmkup;
}

public double getMidt() {
    return midt;
}

public void setMidt(double midt) {
    this.midt = midt;
}

public double getProbs() {
    return probs;
}

public void setProbs(double probs) {
    this.probs = probs;
}

public double getFinex() {
    return finex;
}

public void setFinex(double finex) {
    this.finex = finex;
}

public double getQavg() {
    calcStudent();
    return qavg;
}

public double getCavg() {
    return cavg;
}

private void calcStudent(){
    double[] qs = { q1, q2, q3, q4, q5, qmkup};
    Arrays.sort(qs);
    qavg = (qs[2] + qs[3] + qs [4] + qs[5]) / 4.0;

    if (qavg >= 89.5 && midt >= 89.5 && probs >= 89.5){
        cavg = (qavg+midt+probs) / 3.0;
        lgrade = "A";
    }else{
        cavg = (qavg * .5) + (midt * .15) + (probs * .1) + (finex * .25);
        if (cavg >= 89.5){
            lgrade = "A";
        }else if (cavg >= 79.5){
            lgrade = "B";
        }else if (cavg >= 69.5){
            lgrade = "C";
        }else if (cavg >= 59.5){
            lgrade = "D";
        }else{
            lgrade = "F";
        }
    }
}

@Override
public String toString(){
    String s = sid + "," + lnm + "," + fnm + "," + 
            q1 + "," + q2 + "," + q3 + "," + q4 + "," + q5 + "," + 
            qmkup + "," + midt + "," + probs + "," + finex;

    return s;
}

这是我的java页面:

public class StudentIO {
public static void addStudent(Student s, String path)
             throws IOException{
    File f = new File(path);
    PrintWriter out = new PrintWriter(new FileWriter(f,true));
    out.println(s.toString());
    out.close();
}

public static ArrayList<Student> getStudentList(String path)
              throws IOException {

    BufferedReader in = new BufferedReader
            (new FileReader(path));

    ArrayList<Student> sList = new ArrayList<Student>();
    String line = in.readLine();
    String data[];


    while (line != null){
        data = line.split(",");
        Student s = new Student();

        s.setSid(data[0]);
        s.setLnm(data[1]);
        s.setFnm(data[2]);
        s.setQ1(Double.parseDouble(data[3]));
        s.setQ2(Double.parseDouble(data[4]));
        s.setQ3(Double.parseDouble(data[5]));
        s.setQ4(Double.parseDouble(data[6]));
        s.setQ5(Double.parseDouble(data[7]));
        s.setQmkup(Double.parseDouble(data[8]));
        s.setMidt(Double.parseDouble(data[9]));
        s.setProbs(Double.parseDouble(data[10]));
        s.setFinex(Double.parseDouble(data[11]));

        s.getSid();
        s.getLnm();
        s.getFnm();
        s.getQ1();
        s.getQ2();
        s.getQ3();
        s.getQ4();
        s.getQ5();
        s.getQmkup();
        s.getMidt();
        s.getProbs();
        s.getFinex();

        sList.addAll(Arrays.asList(s));

        line = in.readLine();
        }
    in.close(); 
    return sList;

}

这是我的 servlet:

public class ClassListServlet extends HttpServlet {

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    String emsg = "";
    String path;
    String URL = "/ClassList.jsp";

    ArrayList<Student> stulist;

    try{
        path = getServletContext().getRealPath("/WEB-INF/classlist.txt");
        stulist = StudentIO.getStudentList(path);
        request.setAttribute("stulist", stulist);
    }catch (Exception e){
        emsg = "Process error: " +e.getMessage();
        URL = "/students.jsp";
    }
    RequestDispatcher disp = getServletContext().getRequestDispatcher(URL);
    disp.forward(request, response);
}

这是 JSP 页面:

<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>Class List</title>
</head>
<body>

    <h1>Students on file:</h1>
    <table>
        <tr>    
            <th colspan="12"><br>Class List</th>
        </tr>
        <tr>
            <th colspan="1">Student ID</th>
            <th colspan="1">Last Name</th>
            <th colspan="1">First Name</th>
            <th colspan="1">Quiz 1</th>
            <th colspan="1">Quiz 2</th>
            <th colspan="1">Quiz 3</th>
            <th colspan="1">Quiz 4</th>
            <th colspan="1">Quiz 5</th>
            <th colspan="1">Make-Up Quiz</th>
            <th colspan="1">Midterm</th>
            <th colspan="1">Problems</th>
            <th colspan="1">Final</th>
        </tr>
            <%

                ArrayList<Student> studt = (ArrayList<Student>) 
                                        request.getAttribute("stulist");

                for (int i = 0; i < studt.size(); i++) {
            %>
        <tr>
            <td><%= studt.get(i) %></td>
        </tr>


            <% } %>
    </table>
    <% 
       //cells and titles for each output field     
       //every time through loop will process each individual
       //student object instead of string objects
    %>
</body>

Answer 1

问题出在 getStudentList() 方法中，您不需要每次都创建一个新的 ArrayList。

sList = new ArrayList<Student>(); 

必须移出 while 循环