import org.w3c.dom.*;
import org.apache.xerces.parsers.DOMParser;

class Grades
{ 
    static float grades[][] = new float[100][5];
    static int nstudent = 0;
    static int gi = -1;

    public static void computeGrades(String uri)
	{
	    try {
		DOMParser parser = new DOMParser();
		parser.parse(uri);
		Document doc = parser.getDocument();
		traverse_tree(doc);
		compute_final_grades();
	    } catch (Exception e) {
		e.printStackTrace(System.err);
	    }
	}

    private static void compute_final_grades()
	{
	    float Ave = 0;
	    int i = 0, j = 0;
	    System.out.println("Grades");
	    for(i = 0; i < nstudent ; i++) {
	      float total = 0;
	      for(j = 0; j < 4; j++) {
		  total += grades[i][j];
	      }		
	      grades[i][4] = total/4;
	      Ave += grades[i][4];
	      System.out.println("Student " + i + "=" + grades[i][4]);
	    }
	    Ave /= nstudent;
	    System.out.println("Class Average =" + Ave);  
	}
    private static void traverse_tree(Node node)
	{
	    if(node == null) {
		return;
	    }
	    int type = node.getNodeType();
	    switch (type) {
	    case Node.DOCUMENT_NODE: {
		traverse_tree(((Document)node).getDocumentElement());
		break;
	    }
	    case Node.ELEMENT_NODE: {
		String elementName = node.getNodeName();
		gi = -1;
		if(elementName.equals("hw1"))
		    gi = 0;
		else if(elementName.equals("hw2"))
		    gi = 1;
		else if(elementName.equals("project"))
		    gi = 2;
		else if(elementName.equals("final"))
		    gi = 3;
		else if(elementName.equals("student"))
		    nstudent++;

		NodeList childNodes = node.getChildNodes();	
		if(childNodes != null) {
		    int length = childNodes.getLength();
		    for (int loopIndex = 0; loopIndex < length ; loopIndex++)
		    {
			traverse_tree(childNodes.item(loopIndex));
		    }
		}
		break;
	    }
	    case Node.TEXT_NODE: {
		String chData = node.getNodeValue().trim();
		if(chData.indexOf("\n") < 0 && chData.length() > 0) {
		    if(gi >= 0)
			grades[nstudent-1][gi] = Integer.parseInt(chData);
		}
	    }
	    }
	}
}

public class DOMGrades
{

    public static void main(String[] args)
	{
	    Grades.computeGrades(args[0]);
	}
}


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<?xml version="1.0"?>
     <course>
        <name id="csci_2962">Programming XML in Java</name>
        <teacher id="jp">
           <name>John Punin</name>
        </teacher>
        <student id="js">
           <name>John Smith</name>
           <hw1>30</hw1>
           <hw2>70</hw2>
           <project>80</project>
           <final>85</final>
        </student>
        <student id="gl">
           <name>George Lucas</name>
           <hw1>80</hw1>
           <hw2>90</hw2>
           <project>100</project>
           <final>40</final>
        </student>                                          
        <student id="lr">
           <name>Elizabeth Roberts</name>
           <hw1>60</hw1>
           <hw2>95</hw2>
           <project>50</project>
           <final>90</final>
        </student>
     </course>