Using an arrayList to create a menu and using a text file as input(bufferedReader)

As you can see below I tried creating a switch case for choices
1. Name
2. Course then Name
3. Year Level then Name
4. Course then Year Level and the Name
5. Exit
I don't know how to use switch case so that I could sort everything according to the menu. I will be using comparable and I am only allowed to edit the method called compareTo. My mind is blank and I got no idea where to start.
20192215
Ang
Bryan
m
BSCS
4
20192200
Santos
Charlie
m
BSIT
2
20192452
Chua
Leah
f
BSIS
4
20190012
Yee
John
m
BSCS
2

These are the inputs from text file

    import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.FileReader;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Scanner;
import java.util.Vector;
public class Main {
/**
* @param args the command line arguments
*/
public static void main(String[] args) throws IOException {
try {
BufferedReader br = new BufferedReader(new FileReader("c://student.txt"));
char g;
int yl, I;
String ln, fn, id, cors, con;
Student v[] = new Student[4];
Scanner sc= new Scanner(System.in);
boolean en = true;
boolean ent = true;
for(i = 0; i < 4; i++){
id = br.readLine();
ln = br.readLine();
fn = br.readLine();
g = br.readLine().charAt(0);
cors = br.readLine();
yl = Integer.parseInt(br.readLine());
v[i] = new Student(ln, fn, id, cors, g, yl);
}
while(en == true){
System.out.println("--------------------------------------");
System.out.println("--------------------------------------");
System.out.println("1. Name");
System.out.println("2. Course then Name");
System.out.println("3. Year Level then Name");
System.out.println("4. Course then Year Level and the Name");
System.out.println("5. Exit");
System.out.println("--------------------------------------");
System.out.println("--------------------------------------");
System.out.println("Choose Menu: ");
int choice = sc.nextInt();
switch(choice){
case 1 :
Arrays.sort(v);
display_array(v);
break;
case 2 :
Arrays.sort(v);
display_array(v);
break;
case 3 :
Arrays.sort(v);
display_array(v);
break;
case 4 :
Arrays.sort(v);
display_array(v);
break;
case 5 :
en = false;
System.out.println("\n\n \nTHANK YOU FOR USING THE PROGRAM!!");
break;
}
if(en != false){
System.out.println("Press [Enter key] to continue");
try{
System.in.read();
}catch(Exception e){
e.printStackTrace();
}
}
}
} catch (FileNotFoundException e) {
System.err.println("File not found");
} catch (IOException e) {
System.err.println("Unable to read the file.");
}
}
public static void display_array(Student arr_v[]) throws IOException{
System.out.println("--------------------------------------");
for(int i = 0; i < arr_v.length; i++){
arr_v[i].display();
}
System.out.println("--------------------------------------");
}
}```
```
public class Student implements Comparable {
private String lastname, firstname, studentid, course;
private char gender;
private int yearlevel;
public Student(String ln, String fn, String id, String cors, char g, int yl) {
lastname = ln;
firstname = fn;
studentid = id;
course = cors;
gender = g;
yearlevel = yl;
}
public int compareTo(Object anotherObject) {
Student anotherStudent = (Student) anotherObject;
int compareResult =         
this.course.compareTo(anotherStudent.lastname); 
if(compare )
return 0;  
}
public void display() {
System.out.printf("ID: %-8s  Name: %-20s  Sex: %c  Course: %-8s  Year: %d\n", studentid, (lastname + ", " + firstname), gender, course, yearlevel );
}
public void setGender(char gender){
this.gender = gender;
}
public char getGender(){
return gender;
}
public void setLastname(String lastname){
this.lastname = lastname;
}
public String getLastname(){
return lastname;
}
public void setFirstname(String firstname){
this.firstname = firstname;
}
public String getFirstname() {
return firstname;
}
public void setStudentId(String studentid){
this.studentid = studentid;
}
public String getStudentId(){
return studentid;
}
public void setCourse(String course){
this.course = course;
}
public String getCourse(){
return course;
}
public void setYearLevel(int yearlevel){
this.yearlevel = yearlevel;
}
public int getYearLevel(){
return yearlevel;
}
}```
</details>
# 答案1
**得分**: 0
所有程序员都需要学会如何调试他们的代码。如果你正在使用集成开发环境（IDE），我建议你学习如何使用它的调试器。
在下面的代码中，你有一些不需要的`readLine()`方法调用。在下面的代码中，我已经将这些行标记为注释。我还将`display_array()`和`main()`方法整合到了`Student`类中，只是为了让所有内容都在一个类中，但你不一定非要这样做。
```java
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
public class Student {
private String lastname, firstname, studentid, course;
private char gender;
private int yearlevel;
public Student(String id, String ln, String fn, char g, String cors, int yl) {
studentid = id;
lastname = ln;
firstname = fn;
gender = g;
course = cors;
yearlevel = yl;
}
private static void display_array(Student[] v) {
for (Student s : v) {
s.display();
}
}
public void display() {
System.out.println("Name      : " + lastname + ", " + firstname);
System.out.println("Student ID: " + studentid);
System.out.println("Course    : " + course);
System.out.println("Gender    : " + gender);
System.out.println("Year Level: " + yearlevel);
}
public void setGender(char gender){
this.gender = gender;
}
public char getGender(){
return gender;
}
public void setLastname(String lastname){
this.lastname = lastname;
}
public String getLastname(){
return lastname;
}
public void setFirstname(String firstname){
this.firstname = firstname;
}
public String getFirstname() {
return firstname;
}
public void setStudentId(String studentid){
this.studentid = studentid;
}
public String getStudentId(){
return studentid;
}
public void setCourse(String course){
this.course = course;
}
public String getCourse(){
return course;
}
public void setYearLevel(int yearlevel){
this.yearlevel = yearlevel;
}
public int getYearLevel(){
return yearlevel;
}
public static void main(String[] args) {
try (BufferedReader br = new BufferedReader(new FileReader("c:\\student.txt"));) {
char g;
int yl;
int i;
String ln;
String fn;
String id;
String cors;
Student v[] = new Student[Integer.parseInt(br.readLine())];
//            br.readLine();
for (i = 0; i < v.length; i++) {
id = br.readLine();
ln = br.readLine();
fn = br.readLine();
//                g = (char) br.read();
g = br.readLine().charAt(0);
cors = br.readLine();
yl = Integer.parseInt(br.readLine());
//                if ((br.readLine()) != null)
//                    br.readLine();
v[i] = new Student(id, ln, fn, g, cors, yl);
}
display_array(v);
}
catch (FileNotFoundException e) {
System.err.println("File not found");
}
catch (IOException e) {
System.err.println("Unable to read the file.");
}
}
}

我还修改了student.txt文件。根据你的代码，文件的第一行应该是文件中学生的数量。在你的问题中的示例文件中，有四名学生。

4
20192215
Ang
Bryan
m
BSCS
4
20192200
Santos
Charlie
m
BSIT
2
20192452
Chua
Leah
f
BSIS
4
20190012
Yee
John
m
BSCS
2

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

public class Student {
    private String lastname, firstname, studentid, course;
    private char gender;
    private int yearlevel;

    public Student(String id, String ln, String fn, char g, String cors, int yl) {
        studentid = id;
        lastname = ln;
        firstname = fn;
        gender = g;
        course = cors;
        yearlevel = yl;
    }

    private static void display_array(Student[] v) {
        for (Student s : v) {
            s.display();
        }
    }

    public void display() {
        System.out.println("Name      : " + lastname + ", " + firstname);
        System.out.println("Student ID: " + studentid);
        System.out.println("Course    : " + course);
        System.out.println("Gender    : " + gender);
        System.out.println("Year Level: " + yearlevel);
    }

    public void setGender(char gender){
        this.gender = gender;
    }

    public char getGender(){
        return gender;
    }

    public void setLastname(String lastname){
        this.lastname = lastname;
    }

    public String getLastname(){
        return lastname;
    }

    public void setFirstname(String firstname){
        this.firstname = firstname;
    }

    public String getFirstname() {
        return firstname;
    }

    public void setStudentId(String studentid){
        this.studentid = studentid;
    }

    public String getStudentId(){
        return studentid;
    }

    public void setCourse(String course){
        this.course = course;
    }

    public String getCourse(){
        return course;
    }

    public void setYearLevel(int yearlevel){
        this.yearlevel = yearlevel;
    }

    public int getYearLevel(){
        return yearlevel;
    }

    public static void main(String[] args) {
        try (BufferedReader br = new BufferedReader(new FileReader("c:\\student.txt"));) {
            char g;
            int yl;
            int i;
            String ln;
            String fn;
            String id;
            String cors;
            Student v[] = new Student[Integer.parseInt(br.readLine())];
//            br.readLine();
            for (i = 0; i < v.length; i++) {
                id = br.readLine();
                ln = br.readLine();
                fn = br.readLine();
//                g = (char) br.read();
                g = br.readLine().charAt(0);
                cors = br.readLine();
                yl = Integer.parseInt(br.readLine());
//                if ((br.readLine()) != null)
//                    br.readLine();

                v[i] = new Student(id, ln, fn, g, cors, yl);
            }
            display_array(v);
        }
        catch (FileNotFoundException e) {
            System.err.println("File not found");
        }
        catch (IOException e) {
            System.err.println("Unable to read the file.");
        }
    }
}

4
20192215
Ang
Bryan
m
BSCS
4
20192200
Santos
Charlie
m
BSIT
2
20192452
Chua
Leah
f
BSIS
4
20190012
Yee
John
m
BSCS
2

答案2

得分: 0

public final class Student {

    private final String id;
    private final String firstName;
    private final String lastName;
    private final char gender;
    private final String course;
    private final int yearLevel;

    public Student(String id, String firstName, String lastName, char gender, String course, int yearLevel) {
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
        this.gender = Character.toUpperCase(gender);
        this.course = course;
        this.yearLevel = yearLevel;
    }

    public void display(PrintStream out) {
        out.format("姓名         : %s, %s\n", lastName, firstName);
        out.format("学生编号     : %s\n", id);
        out.format("课程         : %s\n", course);
        out.format("性别         : %s\n", gender);
        out.format("年级         : %d\n", yearLevel);
    }

}

public static void main(String... args) throws FileNotFoundException {
    File file = new File("c://student.txt");
    List<Student> students = readStudents(file);
    display(students);
}

private static List<Student> readStudents(File file) throws FileNotFoundException {
    try (Scanner scan = new Scanner(file)) {
        List<Student> students = new ArrayList<>();

        while (scan.hasNext()) {
            String id = scan.next();
            String lastName = scan.next();
            String firstName = scan.next();
            char gender = scan.next().charAt(0);
            String course = scan.next();
            int yearLevel = scan.nextInt();
            students.add(new Student(id, firstName, lastName, gender, course, yearLevel));
        }

        return students;
    }
}

private static void display(List<Student> students) {
    System.out.println("--------------------------------------");
    System.out.println("--------------------------------------");
    System.out.println("1. 姓名");
    System.out.println("2. 课程再加姓名");
    System.out.println("3. 年级再加姓名");
    System.out.println("4. 课程再加年级和姓名");
    System.out.println("5. 退出");
    System.out.println("--------------------------------------");
    System.out.println("--------------------------------------");

    students.forEach(student -> {
        student.display(System.out);
        System.out.println();
    });
}

public final class Student {
private final String id;
private final String firstName;
private final String lastName;
private final char gender;
private final String course;
private final int yearLevel;
public Student(String id, String firstName, String lastName, char gender, String course, int yearLevel) {
this.id = id;
this.firstName = firstName;
this.lastName = lastName;
this.gender = Character.toUpperCase(gender);
this.course = course;
this.yearLevel = yearLevel;
}
public void display(PrintStream out) {
out.format("Name       : %s, %s\n", lastName, firstName);
out.format("Student ID : %s\n", id);
out.format("Course     : %s\n", course);
out.format("Gender     : %s\n", gender);
out.format("Year Level : %d\n", yearLevel);
}
}
public static void main(String... args) throws FileNotFoundException {
File file = new File("c://student.txt");
List<Student> students = readStudents(file);
display(students);
}
private static List<Student> readStudents(File file) throws FileNotFoundException {
try (Scanner scan = new Scanner(file)) {
List<Student> students = new ArrayList<>();
while (scan.hasNext()) {
String id = scan.next();
String lastName = scan.next();
String firstName = scan.next();
char gender = scan.next().charAt(0);
String course = scan.next();
int yearLevel = scan.nextInt();
students.add(new Student(id, firstName, lastName, gender, course, yearLevel));
}
return students;
}
}
private static void display(List<Student> students) {
System.out.println("--------------------------------------");
System.out.println("--------------------------------------");
System.out.println("1. Name");
System.out.println("2. Course then Name");
System.out.println("3. Year Level then Name");
System.out.println("4. Course then Year Level and the Name");
System.out.println("5. Exit");
System.out.println("--------------------------------------");
System.out.println("--------------------------------------");
students.forEach(student -> {
student.display(System.out);
System.out.println();
});
}