public class Exam {

	private int[] scores; // student scores on this exam
	private int size; // = # of scores = next availale slot
	private int capacity; // = max number of scores

	public Exam() {
		super();
		capacity = 100;
		size = 0;
		scores = new int[capacity];
	}

	private void validateIndex(int index) {
		if(index < 0 || size <= index) {
			System.out.println("Error: array index out of range!");
			System.exit(1); // shut program down!
		}
	}

	public int getScore(int index) {
		validateIndex(index);
		return scores[index];
	}

	public int getSize() {
		return size;
	}

	public void addScore(int score) {
		if (size < capacity) {
			scores[size] = score;
			size = size + 1;
		}
	}

	public double getAverage() {
		double result = 0.0;
		int index = 0;
		while(index < size) {
			result = result + scores[index];
			index = index + 1;
		}
		if (0 < size) {
			result = result/size;
		} else {
			result = 0;
		}

		return result;
	}
}