package student;

public class Student
{
    private int number;
    private String name;
    private int grade;

    public Student(int number, String name, int grade)
    {
        this.number = number;
        this.name = name;
        this.grade = grade;
    }

    public Student(int number)
    {
        this.number = number;
        this.name = "";
        this.grade = 0;
    }

    public int getNumber()
    {
        return number;
    }

    public void setNumber(int number)
    {
        this.number = number;
    }

    public String getName()
    {
        return name;
    }

    public void setName(String name)
    {
        this.name = name;
    }

    public int getGrade()
    {
        return grade;
    }

    public void setGrade(int grade)
    {
        this.grade = grade;
    }

    public boolean equals(Student student)
    {
        return getNumber() == student.getNumber();
    }

    public String toString()
    {
        return getNumber() + " " + getName() + " " + getGrade();
    }
}

package student;

import java.util.*;

public class StudentDB  {

	private static final int  INITIAL_SIZE = 5;

	private static int  studNum = 0;

        private Student[] course;

	public StudentDB()  {

                course = new Student[INITIAL_SIZE];
		studNum = 0;
	}

	public void addStudent(Student student)  {

            if (! checkStudent(student)) {
		int studAdded = getStudNum();

                if (studAdded == course.length) {

		     Student[] newCourse;

                     newCourse = new Student[course.length*2];

                     for (int i = 0; i < course.length ; i++)
			newCourse[i] = course[i];	 

                     course = newCourse;
                }

                course[studNum++] = student;
             }
	}

	public boolean checkStudent(Student student)  {
	
		for (int i = 0; i < getStudNum(); i++)
			if (course[i].equals(student))
				return true;
		return false; 
	}

	public Student lookUpStudent(Student student)  {
	
		for (int i = 0; i < getStudNum(); i++)
			if (course[i].equals(student))
				return course[i];
		return null; 
	}

	public void sortStudentByMark()  {

		for (int i = 0; i < getStudNum(); i++)
			for (int j = getStudNum() - 1; i < j; j--) {
			   if (course[j-1].getGrade() > course[j].getGrade()) {
				Student temp = course[j-1];
				course[j-1] = course[j];
				course[j] = temp;
			    }
			}
	}

	public String toString()  {

		String s = "";

                for (int i = 0; i < getStudNum() ; i++)
			s = s + course[i].toString() + '\n' ;	 

		return s;
	}

        private static int getStudNum() {
		return studNum;
	}

}