Java

OOP GUIDE / WORK

STUDENT CLASS 2 SOLUTIONS

TASK – PART 1 – SETUP

No solutions required.

TASK – PART 2 – SORTING BASED ON A COMPARE MODE

Below is my solution. Note that I opted to create three methods that I call from inside the compareTo method to keep things organized. Also, to avoid having to remember which mode number is which one, I create three static methods that can be used to set the mode value.

public class Student implements Comparable

{

public String lastName;

public String firstName;

public int grade;

public String school;

public static int compareMode; //all students share one static var

public Student()

{

String[] lastNames = {"Smith", "Do", "Bardot", "Lu", "Green", "Lowe", "Bacon", "Zoom", "Gravy", "TwoShoes", "Monroe", "Hope", "West", "Lopez", "Gray"};

lastName = lastNames[(int)(Math.random() * lastNames.length)];

String[] firstNames = {"Jimmy", "June", "Abbott", "Luna", "Harry", "Moon", "Lea", "Kayla", "Aryan", "Grace", "Drake", "Kiana", "Burt", "Amitoj", "Xavier", "Shaun", "Mary"};

firstName = firstNames[(int)(Math.random() * firstNames.length)];

grade = (int)(Math.random() * 4) + 9;

String[] schools = {"Lockerby", "Confed", "Lasalle", "Lo-Ellen"};

school = schools[(int)(Math.random() * schools.length)];

compareMode = 1;

}

public String toString()

{

return grade + " " + firstName + " " + lastName + " (" + school + ")";

}

public static void compareByLastName()

{

compareMode = 1;

}

public static void compareBySchool()

{

compareMode = 2;

}

public static void compareByGrade()

{

compareMode = 3;

}

@Override

public int compareTo(Object o)

{

if (compareMode == 1)

return compareToByLastName(o);

else if (compareMode == 2)

return compareToBySchool(o);

else

return compareToByGrade(o);

}

public int compareToBySchool(Object o)

{

Student other = (Student)o;

return this.school.compareTo(other.school);

}

public int compareToByLastName(Object o)

{

Student other = (Student)o;

return this.lastName.compareTo(other.lastName);

//Note: String's compareTo compares two Strings alphanumerically.

//It returns -1, 0 or 1 in the same way as compareTo does. Very convenient!

//Note: Could improve this to have first name serve as tie breaker.

}

public int compareToByGrade(Object o)

{

Student other = (Student)o;

if (this.grade < other.grade)

return -1;

else if (this.grade == other.grade)

{

return 0;

}

else //this.grade > other.grade

{

return 1;

}

}

}

TASK – PART 3 – TESTING ALL SORTING CRITERIAS

Here is my solution:

import java.util.Arrays;

public class StudentTester

{

public static void main(String[] args)

{

Student[] stews = new Student[20];

//Create students

for (int i=0; i<stews.length; i++)

{

stews[i] = new Student();

}

//Output students

for (int i=0; i<stews.length; i++)

{

System.out.println(stews[i]);;

}

Student.compareByGrade();

Arrays.sort(stews);

System.out.println("=====COMPARE BY GRADE=====");

//Output students

for (int i=0; i<stews.length; i++)

{

System.out.println(stews[i]);;

}

Student.compareByLastName();

Arrays.sort(stews);

System.out.println("=====COMPARE BY LAST NAME=====");

//Output students

for (int i=0; i<stews.length; i++)

{

System.out.println(stews[i]);;

}

Student.compareBySchool();

Arrays.sort(stews);

System.out.println("=====COMPARE BY SCHOOL=====");

//Output students

for (int i=0; i<stews.length; i++)

{

System.out.println(stews[i]);;

}

}

}