how to make fuction to allow me to delete a specific student

Question

i want to add a function that allow me to delete a students
first this is the this the file student.java that contain the class student , then the file called vstudent contain the ittrator and the array list to loop on the all students,then there is a file called Mainsystem contain the files handilling and functions to add students ,so i want to add fuction that allow me to delete a student.

import java.io.*;
import java.util.Scanner;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class student implements Serializable {
    private int id;
    private String name, email;
    private int mobilenumber;

    public student(int id, String name, String email, int mobilenumber) {
        this.id = id;
        this.name=name;
        this.email = email;
        this.mobilenumber = mobilenumber;

    }

    public int getId() {
        return id;
    }

    @Override
    public String toString() {
        return "student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", email='" + email + '\'' +
                ", mobilenumber=" + mobilenumber +
                '}';
    }
}
import java.io.*;
import java.io.File.*;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.io.Serializable;
import java.util.Scanner;
public class vstudent extends Object implements Serializable {
    private List<student> coll;

    public vstudent() {
        coll = new ArrayList<student>();
    }

    public void addstudent(student stu){
        coll.add(stu);
    }

    @Override
    public String toString() {
        String total = "\n";
        Iterator<student> i = coll.iterator();
        while (i.hasNext()){
            student s = (student) i.next();
            total= total+s.toString();
        }
        return total;
    }


} 
import java.util.List;
import java.util.Scanner;
import java.io.Serializable;
import java.io.*;
import java.util.Iterator;




     class librarianmenu {
        public static void librarianMenu() {
            System.out.println("---------------(Librarian) - Library Management System-----------");
            System.out.println("\nEnter 0 for load a library" + "\nEnter 1 for save and quit" + "\nEnter 2 to add book"
                    + "\nEnter 3 to list all books in library" + "\nEnter 4 to list all librarians");
        }
    }

    public  class Mainsystem {
        static String fileName = null;
        static library lib = new library();
        static vstudent stu = new vstudent();
        static librs librs = new librs();
        static Scanner in = new Scanner(System.in);
        static Boolean running = true;
        public static void DisplayMainMenu() {
            System.out.println("------------ Library Management System ------------");
            System.out.println("Enter #: Switch to Admin Mode");
            System.out.println("Enter $: Switch to Student Mode");
            System.out.println("Enter <: Exit");
        }


        public static void main(String[] args) {
            DisplayMainMenu();


            Scanner in = new Scanner(System.in);
            boolean shouldContinue = true;
            while (true) {
                String optionSelected = in.next();
                if (!optionSelected.equals("<")) {
                    if (optionSelected.equals("#")) {
                        Admin admin = new Admin();

                        System.out.print("Enter Password: ");
                        String tempPassword = in.next();
                        System.out.println(tempPassword);

                        if (tempPassword.equals(admin.getPassword())) {
                            boolean isCorrectPassword = true;
                            while (isCorrectPassword) {
                                admin.displayMenu();
                                int adminInput = in.nextInt();
                                switch (adminInput) {
                                    case 0: {
                                        System.out.println("Enter the file name to load");
                                        loadScript(in.next());
                                        break;
                                    }
                                    case 1: {
                                        addstudent();
                                        break;
                                    }
                                    case 2: {
                                        addlibrarians();
                                        break;
                                    }
                                    case 3: {
                                        System.out.println(stu.toString());
                                        break;
                                    }
                                    case 4: {
                                        saveandquit();
                                        break;
                                    }
                                    case 5: {
                                        System.out.print("Enter new password:");
                                        String pass = in.next();
                                        admin.setPassword(pass);
                                        break;
                                    }


                                    case 6: {
                                        isCorrectPassword = false;
                                        DisplayMainMenu();
                                    }
                                }
                            }
                        } else {
                            DisplayMainMenu();
                        }
                    } else if (optionSelected.equals("$")) {
                        librarianmenu menu = new librarianmenu();

                        while (running) {
                            librarianmenu.librarianMenu();
                            int studentInput = in.nextInt();
                            switch (studentInput) {
                                case 0: {
                                    System.out.println("Enter the file name to load");
                                    loadScript(in.next());
                                    break;
                                }
                                case 1: {
                                    saveandquit();
                                    break;
                                }
                                case 2: {
                                    addBook();
                                    break;
                                }
                                case 3: {
                                    System.out.println(lib.toString());
                                    break;
                                }
                                case 4: {
                                    System.out.println(librs.toString());
                                }

                            }
                        }

                    } else { //User chooses to Exit
                        break;
                    }
                }

            }
        }


                    private static void addBook () {
                        int id;
                        String title, author;
                        int Available_quantity;
                        int issued_quantity;
                        System.out.println("\nEnter book name");
                        title = in.next();
                        System.out.println("\nEnter book Author");
                        author = in.next();
                        System.out.println("\nEnter book id");
                        id = in.nextInt();
                        System.out.println("\nEnter Available quantity");
                        Available_quantity = in.nextInt();
                        System.out.println("\nEnter issued_quantity");
                        issued_quantity = in.nextInt();
                        Book b = new Book(id, title, author, Available_quantity, issued_quantity);
                        lib.addBook(b);


                    }

                    private static void addstudent () {
                        int id;
                        String name, email;
                        int mobilenumber;
                        System.out.println("\nEnter student name");
                        name = in.next();
                        System.out.println("\nEnter student email");
                        email = in.next();
                        System.out.println("\nEnter student id");
                        id = in.nextInt();
                        System.out.println("\nEnter mobile number ");
                        mobilenumber = in.nextInt();
                        student s = new student(id, name, email, mobilenumber);
                        stu.addstudent(s);

                    }

                    private static void addlibrarians () {
                        int id;
                        String name;
                        int password;
                        System.out.println("\nEnter librarian name");
                        name = in.next();
                        System.out.println("\nEnter librarian id");
                        id = in.nextInt();
                        System.out.println("\nEnter password ");
                        password = in.nextInt();
                        librarians libras = new librarians(id, name, password);
                        librs.addlibrs(libras);

                    }

                    private static void saveandquit () {
                        System.out.println("Enter file name:");
                        fileName = in.next() + ".ser";
                        running = false;
                        FileOutputStream fos = null;
                        ObjectOutputStream out = null;
                        try {
                            fos = new FileOutputStream(fileName);
                            out = new ObjectOutputStream(fos);
                            out.writeObject(lib);
                            out.writeObject(stu);
                            fos.close();
                            out.close();
                        } catch (FileNotFoundException e) {
                            e.printStackTrace();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }

                    }

                    private static void loadScript (String name){
                        FileInputStream fis = null;
                        ObjectInputStream in = null;
                        File file = new File(name + ".ser");
                        if (file.exists()) {
                            try {
                                fis = new FileInputStream(file);
                                in = new ObjectInputStream(fis);
                                try {
                                    lib = (library) in.readObject();
                                    stu = (vstudent) in.readObject();

                                } catch (ClassNotFoundException e) {
                                    e.printStackTrace();
                                }
                                fis.close();
                                in.close();
                            } catch (IOException e) {
                                e.printStackTrace();

                            }
                        } else {
                            System.out.println("\nThe file does not exist!");
                        }
                    }
                }

Answer 1

As I can see , You use List from which you want to delete element, In Java if you want to delete element you need to provide its id , Syntax :

StudentList.remove(idStudent)

for you i think you want to find a way to get the ID of the student you want to delete this is a way:

    private static void deleteStudent ()   {
    System.out.println("\nEnter ID of the student you want to delete ");
    idStudent = in.nextInt();
    for( Student st : stu){
        if(st.getID()==idStudent){
            stu.remove(idStudent);
        }
    }
}