public class ArrayOfObjectsDemo
{
	
    public static void main(String[] args)
    {
        Student[] roster = new Student[10];   // instantiate the array
		
        for (int i = 0; i < roster.length; i++)
        {
            roster[i] = new Student();        // instantiate each Student
        }                                     // within the array of Students
		
	    // display all student schedules
        for (int j = 0; j < roster.length; j++)
        {
            System.out.print("\nStudent ID " + roster[j].getID() + ": ");
			
            for (int i = 0; i < roster[j].getSchedule().length; i++)
            {
                System.out.print(roster[j].getSchedule()[i] + " ");
            }
		
        }
		
        // *******************************************************************		
        // How many students are taking Calculus?
        int count = 0;		// # of students taking Calculus
		
        for (int j = 0; j < roster.length; j++)
        {
			
            // Calculus is only offered in index position 2 of a schedule
            if (roster[j].getSchedule()[2].equals("Calculus"))
            {
                count++;
            }
		
        }
		
        System.out.println("\n" + count + " students are taking Calculus");

        // *******************************************************************		
        // How many students are taking a class that begins with the letter H?
        count = 0;      // # of students taking a course that begins with H
		
        // loop through the student roster
        for (int j = 0; j < roster.length; j++) 
        {
			
            // loop through each student's schedule
            for (int i = 0; i < roster[j].getSchedule().length; i++)
            {
				
                if (roster[j].getSchedule()[i].substring(0, 1).equals("H"))
                {
                    count++;
                    break;  // don't count student twice if he is taking both
                            // History and Humanities
                }

            }
		
        }
		
        System.out.println(count + " students are taking a course that begins with H");
    }
	
}

// ************************  Student class ***********************

class Student
{
    // default constructor
    public Student()
    {	
        mySchedule = new String[5];
		
        mySchedule[0] = Math.random() > .5 ? "Chem" : "Bio";
        mySchedule[1] = Math.random() > .5 ? "History" : "Econ";
        mySchedule[2] = Math.random() > .5 ? "Calculus" : "Statistics";
        mySchedule[3] = Math.random() > .5 ? "English" : "Humanities";
        mySchedule[4] = Math.random() > .5 ? "Java" : "Latin";
        // For the AP exam, you don't need to know how to use the
        // ternary/selection operator  ? :
		
        myID = currentID;
        currentID++;      // increment currentID so next Student to be
		                  // instantiated has his own unique ID #
    }
	
    // accessor methods
    public int getID()
    {
        return myID;
    }
	
    public String[] getSchedule()
    {
        return mySchedule;
    }	
	
    // interesting methods
    public void changeSchedule(String newCourse, int period)
    {
        mySchedule[period - 1] = newCourse;
    }
	
    public void makeNewSchedule(String[] newSchedule)
    {
        mySchedule = newSchedule;
    }
	
    // properties
    private static int currentID = 0;  // static property for ID's to be unique
    private int myID;                  // each student has unique ID #
    private String[] mySchedule;
}