Group

* Solution

package ru.sgu.csit;

import java.io.*;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;

public class Solution {

    public static void main(String[] args) throws IOException {
        try(BufferedReader r = new BufferedReader(new FileReader(new File("group.txt"))))
        {
            String str;
            Integer i2 = null;
            ArrayList<Student> student = null;

            Group group = new Group(student, i2);

            SimpleDateFormat dateFormat = new SimpleDateFormat("ddMMYYYY");
            while((str=r.readLine())!=null)
            {
                String[] strParts = str.split(" ");
                if (strParts.length != 1)
                {

                    Integer i1 = 0;

                    try
                    {
                        i1 = new Integer(strParts[0]);
                    }
                    catch (NumberFormatException e)
                    {
                        System.err.println("Неверный формат строки!");
                    }
                    Student b = new Student(strParts[1], strParts[2], strParts[3], i1, dateFormat.parse(strParts[4]));
                    if (group.isEmpty())
                    {
                        ArrayList<Student> arr = new ArrayList<Student>();
                        arr.add(b);
                        group.setStudents(arr);
                    }else
                    group.addStudents(b);
                }
                else
                {
                    if(!group.isEmpty())
                        System.out.println("Саааамый старший студент: " + group.getOldestStudent());
                    else
                        System.out.println("Group of students is empty");

                    group.setId(i2);
                    group.setStudents(student);
                    try
                    {
                        i2 = new Integer(str);
                    }
                    catch (NumberFormatException e)
                    {
                        System.err.println("Неверный формат строки!");
                    }
                    group.setId(i2);
                }
                System.out.println(str);
            }
            if(!group.isEmpty())
                System.out.println("Саааамый старший студент: " + group.getOldestStudent());
            else
                System.out.println("Group of students is empty");

        }
        catch (IOException | ParseException e)
        {
            e.printStackTrace();
        }

    }
}

*Group

package ru.sgu.csit;

import java.util.ArrayList;

public class Group {
    private ArrayList<Student> students;
    private Integer id;

    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public ArrayList<Student> getStudents() {
        return students;
    }
    public void setStudents(ArrayList<Student> students) {
        this.students = students;
    }
    public void addStudents(Student st){
        this.students.add(st);
    }
    public Group(ArrayList<Student> students, Integer id) {
        this.students = students;
        this.id = id;
    }

    public Student getOldestStudent()
    {
        Student maxx = students.get(0);
        for (int i = 1; i < this.students.size();i++) {
            if (maxx.getBirthday().compareTo(students.get(i).getBirthday()) > 0)
            {
                maxx = students.get(i);
            }
        }
        return maxx;
    }

    @Override
    public String toString() {
        return "Group{" +
                "students=" + students +
                ", id=" + id +
                '}';
    }

    public boolean isEmpty()
    {
        if (this.getStudents() == null)
            return true;
        else
            return false;
    }

}

*Student

package ru.sgu.csit;

import java.text.SimpleDateFormat;
import java.util.Date;

public class Student {
    private String lastName;
    private String firstName;
    private String secondName;
    private Integer studentId;
    private Date birthday;

    public Date getBirthday() {
        return birthday;
    }

    public Student(String Name, String FName, String SName, Integer Id, Date DR) {
        this.lastName = Name;
        this.firstName = FName;
        this.secondName = SName;
        this.studentId = Id;
        this.birthday = DR;
    }

    @Override
    public String toString() {
        SimpleDateFormat DataFormat = new SimpleDateFormat("ddMMYYYY");
        //DataFormat.format(new Date())
        return this.studentId + " " + this.lastName + " " + this.firstName + " " + this.secondName + " " + DataFormat.format(this.birthday);
    }

}