Класс Vector

public class Student {
    private User[] base = new User[10];
    private int size;
 
    public void addUser(String firstName, String middleName, String lastName, String birthDay, float srBal) {
        this.base[size++] = new User(firstName, middleName, lastName, birthDay, srBal);
    }
 
    public int countUser() {
        return size;
    }
 
    public void deleteUser(String firstName, String middleName, String lastName) {
        if (size != 0) {
            for (int i = 0; i < this.size; i++) {
                User user = base[i];
                if (user.firstName.equals(firstName) && user.middleName.equals(middleName) && user.lastName.equals(lastName)) {
                    base[i] = null;
                    System.arraycopy(this.base, 1, this.base, 1, this.base.length - 1);
                    this.size--;
                }
            }
        }
    }
 
    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        if (this.size != 0) {
            for (int i = 0; i < this.size; i++) {
                User user = this.base[i];
                sb.append("FIO: ").append(user.firstName).append(" ").append(user.middleName).append(" ").append(user.lastName).append("; ");
                sb.append("Date: ").append(user.birthDay.toString()).append("; ").append("Sredniy ball: ").append(user.srBal).append("; ");
                sb.append(System.lineSeparator());
            }
        }
        return sb.toString();
    }
 
    private class User {
        String firstName;
        String middleName;
        String lastName;
        String birthDay;
        float srBal;
 
        public User(String firstName, String middleName, String lastName) {
            this.firstName = firstName;
            this.middleName = middleName;
            this.lastName = lastName;
        }
 
        public User(String firstName, String middleName, String lastName, String birthDay, float srBal) {
            this(firstName, middleName, lastName);
            this.birthDay = birthDay;
            this.srBal = srBal;
        }
    }
}
 
class MainClass {
    public static void main(String[] args) {
        Student base = new Student();
        base.addUser("выф", "пав", "пва", "4.14.2021", 4.5f);
        base.addUser("Гавы", "Мрппа", "Олвыч", "1.12.2001", 4.6f);
        base.addUser("Ворон", "Овыг", "пывыч", "13.7.2001", 3.7f);
        base.addUser("Спав", "асв", "Брпа", "6.9.1999", 4.2f);
        base.addUser("рпа", "рпа", "рап", "4.3.2001", 4.6f);
        System.out.println(base.countUser());
        System.out.println(base.toString());
 
    }
}