import org.w3c.dom.*;
import java.util.*;

/**
 * This object tracks a student's classes and grades
 * received. An instance of this class knows both how
 * to create itself from and represent itself as a
 * DOM tree.
 */
public class Grades implements java.io.Serializable {
	protected Vector _svClassDesc = null;
	public Vector _svGrade = null;
/**
 * Grades constructor comment.
 */
public Grades() {
	super();
}
/**
 * Append a grade to the list of class descriptions
 * @param sGrade java.lang.String
 */
public void addClassDesc(String sClassDesc) {
	_svClassDesc.addElement(sClassDesc);
}
/**
 * Append a grade to the list of grades
 * @param sGrade java.lang.String
 */
public void addGrade(String sGrade) {
	_svGrade.addElement(sGrade);
}
/**
 * Return a document fragment representing this object.
 * We're simply going to do
 *   <GRADE VALUE="A">Description of class</GRADE> for all grades.
 * @return org.w3c.dom.DocumentFragment
 */
public org.w3c.dom.DocumentFragment getAsDOM(Document doc) {
	DocumentFragment dfResult = doc.createDocumentFragment();

	dfResult.appendChild(doc.createComment("Begin Grades.getAsDOM()"));
	
	for (int i = 0; i < iGradeCount(); i++) {
		
		Element e = doc.createElement("GRADE");
		e.setAttribute("VALUE", getGrade(i));
		
		Text textDesc = doc.createTextNode(getClassDesc(i));
		
		e.appendChild(textDesc);
		
		dfResult.appendChild(e);
	}
	dfResult.appendChild(doc.createComment("End Grades.getAsDOM()"));

	return dfResult;
}
/**
 * Return the description of class i.
 * @return java.lang.String
 * @param i int
 */
public String getClassDesc(int i) {
	return (String)(_svClassDesc.elementAt(i));
}
/**
 * Return the grade received in the class. Blank if
 * class is in progress.
 * @param i int
 */
public String getGrade(int i) {
	return (String)(_svGrade.elementAt(i));
}
/**
 * Return the grade point average for all grades.
 * A=4, B=3, C=2, D=1, F=0.
 * @return double
 */
public double getGradePointAverage() {
	int i = 0;
	double total = 0.0;
	
	for (i = 0; i < iGradeCount(); i++) {
		String sGrade = getGrade(i);
		if (sGrade.length() > 0) {
			switch (getGrade(i).charAt(0)) {
				case 'A' :
					total += 4;
					break;
				case 'B' :
					total += 3;
					break;
				case 'C' :
					total += 2;
					break;
				case 'D' :
					total += 1;
					break;
			}
		}
	}
	
	if (i > 0) {
		return total / i;
	} else {
		return -1.0; 	// Unknown
	}
}
/**
 * Return the number of classes taken
 * @return int
 */
public int iGradeCount() {
	return (_svGrade == null) ? 0 : _svGrade.size();
}
/**
 * Print this object in human-readable format
 */
public void print() {
	System.out.println("Grade\tCourse Description\n-----\t------------------");
	for (int i = 0; i < iGradeCount(); i++) {
		System.out.println(getGrade(i) + "\t\t" + getClassDesc(i));
	}
	System.out.println("End of grade report");
}
/**
 * Initializes this instance based on contents of DOM document tree.
 * @param n org.w3c.dom.Node
 */
public void setAsDOM(Element n) {
	Element topNode = n;

	// We accept <Property NAME="..."><JavaBean CLASS="...">,
	// and also accept <propname CLASS="...">. This little piece of
	// code is just to figure out if we have to eliminate a "<JavaBean>" node.
	if (n.getTagName().equals("Property")) {
		NodeList nl = n.getChildNodes();
		for (int i = 0; i < nl.getLength(); i++) {
			if (nl.item(i) instanceof Element &&
				(((Element) (nl.item(i))).getTagName().equals("JavaBean")))
				topNode = (Element) (nl.item(i));
		}
	}


	// Clear out any old values, or create for the first time
	_svGrade = new Vector();
	_svClassDesc = new Vector();

	// For each element, get the grade and description and set them
	NodeList kids = topNode.getChildNodes();
	for (int i = 0; i < kids.getLength(); i++) {
		Node nThisNode = kids.item(i);

		// Be sure it's a "GRADE" Element
		if (!(nThisNode instanceof Element))
			continue;
		Element eThisElem = (Element) nThisNode;
		if (!eThisElem.getTagName().toUpperCase().equals("GRADE"))
			continue;

		// Get grade and description
		String sGrade = eThisElem.getAttribute("VALUE");

		// If the first node isn't Text, ignore it.
		nThisNode = eThisElem.getFirstChild();
		if (!(nThisNode instanceof Text))
			continue;
		String sClassDesc = ((Text) nThisNode).getData();
		addGrade(sGrade);
		addClassDesc(sClassDesc);
	}
}
/**
 * Set description for class number i
 * @param i int
 */
public void setClassDesc(int i, String s) {
	if (_svClassDesc.size() < i) {
		_svClassDesc.setSize(i + 1);
	}
	_svClassDesc.setElementAt(s, i);
}
/**
 * Set grade for class number i
 * @param i int
 */
public void setGrade(int i, String s) {
	if (_svGrade.size() < i) {
		_svGrade.setSize(i + 1);
	}
	_svGrade.setElementAt(s, i);
}
}