Using empty arrays to create methods

Question

Thanks to some online assistance from the wonderful stackoverflow users, here is the edits to the enroll and drop student methods to add to the Student array set up. Now it's just on to get the other methods to work as well. Any insight for those would be helpful, especially for speed and efficiency at those points.

import java.util.Scanner;

public class School {

private Student[] theStudents;

public School() {
    this.theStudents = new Student[] { null };// needs to start out as empty

}

/*
 * next two methods would allow a user to add or drop a student into the
 * student array for the school Also with Enroll student, should be able to
 * assign a class to the student, i.e. Calculas, history, etc
 */
public void enrollStudent(Student newStudent) {
    Student newStudents[] = new Student[theStudents.length+1];
    for (int i = 0; i < theStudents.length; i++)
    {
        newStudents[i] = theStudents[i];
    }
    newStudents[theStudents.length] = newStudent;
    theStudents = newStudents;
}

public void dropStudent(Student dropStudent) {
    Student newStudents[] = new Student[theStudents.length-1];
    for (int i = 0; i > theStudents.length; i--)
    {
        newStudents[i] = theStudents[i];
    }
    newStudents[theStudents.length] = dropStudent;
}

// add Test Score for a student
public double addTestScore(String newStudent, double testScore) {
    testScores[posi] = testScore;
}

/*
 * count the number of students in a given class, not the school
 */
public int countClassSize(String course) {

}

// get average average score of a given class
public double averageAverageScore(String course) {

}

/*
 * add a programming language to only CS students at the school Will need to
 * use the instanceof for proper type casting
 */
public String addProgrammingLanguage(String studentName, String programLanguage) {

}

/*
 * Count the number of students in the school that know a certain
 * programming language, again will need to typecast properly
 */
public int numberThatKnowLanguage(String programLanguage) {

}

public static void main(String[] args) {
    // TODO Auto-generated method stub
    Scanner input = new Scanner(System.in);
    String dropStudent, course;

    System.out.println("Welcome to the School. Please select " + "Option 1 to enroll a regular student, \n "
            + "Option 2 to enroll a CompSci student, \n" + "Option 3 to drop a student, \n"
            + "Option 4 to add test score or programming language, or \n" + "Option 5 to perform class analytics.");
    int Operation = input.nextInt();

    /*
     * Simple UI to add and drop students, will need to set the operation to
     * call the add and drop students to fit them to the Student body array
     * will need to make these two options loop until the user is satisfied
     * with the size of the student body
     */
    if (Operation == 1) {
        System.out.println("Enter the # of regular students that you want to add to the school.");
        int addStudents = input.nextInt();
        /*
         *  Possibly create some type of input array to 
         *  make it easier to enter the students' names
         */
        System.out.println("Please enter the name and course of the student you are enrolling:");
        Student newRegularStudent = (String) input.next();
        course = input.next();
    }

    else if (Operation == 2) {
        System.out.println("Enter the # of CompSci students that you want to add to the school.");
        int addStudents = input.nextInt();
        /*
         * Possibly create some type of input array to make it easier to
         * enter the students' names
         */
        System.out.println("Please enter the name and course of the student you are enrolling:");
        Student newCompSciStudent = (String) input.next();
        course = input.next();
    }

    else if (Operation == 3) {
        System.out.println("Enter the # of students that you want to drop from the school.");
        int dropStudents = input.nextInt();
        /*
         * Possibly create some type of input array to make
         *  it easier to enter the students' names
         */
        System.out.println("Please enter the name of the student you wish to drop from the school:");
        dropStudent = (String) input.next();

        /*
         * After the first two operations, will need to build to the UI to
         * call the other five methods, will need to make it into a
         * while/for loop so user can continue to add information as needed.
         */
    }

    else if (Operation == 4) {
        System.out.println("Enter the # for what you want to add to a student's records."
                + "Enter 1 to enter a test score\n   " + "Enter 2 to enter a programming language, enter 2.");
        int optionNum1 = input.nextInt();
        /*
         *  Possibly create some type of input array 
         *  to make it easier to enter the students' names
         */
        if (optionNum1 == 1) {

        } else if (optionNum1 == 2) {

        }
    }

    else if (Operation == 5) {
        System.out.println("This is the analytics section of this program.\n");

        System.out.println("Enter the # for which of the following analytics options that you want performed: "
                + "Enter 1 to count the # of students for a particular class,\n "
                + "Enter 2 to calculate the average average score for all students take a particular course, or\n "
                + "Enter 3 to count the # of CompSciStudents.");
        int optionNum2 = input.nextInt();
        if (optionNum2 == 1) {
            System.out.println("Enter the course name that you want to know the # of students for.");
            course = input.next();
            Student classSize;
            classSize.countClassSize(course);
        }

        else if (optionNum2 == 2) {
            System.out.println("Enter the course name that you want \n"
                    + "to calculate the average average test value for.");
            course = input.next();
            Student testAvg;
            testAvg.averageAverageScore(course);
        }

        else if (optionNum2 == 3) {
            System.out.println("Count the # of CompSciStudents who know a \n"
                    + "particular programming language by entering that language name now.");
            String programLanguage = input.next();
            CompSciStudent csStudent;
            csStudent.knowsLanguage(programLanguage);
        }
    }
    input.close();
}

}

Answer 1

I don't know if this is the best way, but if I were you, I would just create a new array one size larger or smaller and fill it will the values from the old array each time you add or remove a value. For example:

public void enrollStudent(Student newStudent) {
    Students newStudents[] = new Student[theStudents.length+1];
    for (int i = 0; i < theStudents.length; i++)
    {
        newStudents[i] = theStudents[i];
    }
    newStudents[theStudents.length] = newStudent;
    theStudents = newStudents;
}

Not very efficient but hey, it doesn't sound like you're doing anything that needs to be super efficient.