public class StudentNode extends Student
{

    private StudentNode next;

    public StudentNode(int number, String name, int grade)
    {
        super(number, name, grade);
        this.next = null;
    }

    public StudentNode(int number)
    {
	super(number, "", 0);
        this.next = null;
    }

    public StudentNode getNext()
    {
        return next;
    }

    public void setNext(StudentNode next)
    {
        this.next = next;
    }

    public boolean equals(Object obj)
    {
        if(obj instanceof StudentNode)
        {
            StudentNode studentNode = (StudentNode)obj;
            return getNumber() == studentNode.getNumber();
        } else
        {
            return false;
        }
    }

    public int compareTo(Object obj)
        throws ClassCastException
    {
        int i = getGrade();
        int j = ((StudentNode)obj).getGrade();
        return i != j ? i >= j ? 1 : -1 : 0;
    }
}

public class LinkedListStudentDB  {

        private StudentNode sList;

	public LinkedListStudentDB()  {

                sList = null;

	}

	public void addStudent(StudentNode studentNode)  {

            if (! checkStudent(studentNode)) {

                if (sList == null) 
		     sList = studentNode;
                else {
                     StudentNode p = sList;

                     while ((p != null) && (p.compareTo(studentNode) > 0)) 
                           p = p.getNext();

                     if (p == sList) {
                        studentNode.setNext(sList);
                        sList = studentNode;
                     } else {
                            StudentNode q = sList;
                            while (q.getNext() !=  p) 
                                   q = q.getNext();
                            			
                            q.setNext(studentNode);
                            studentNode.setNext(p);
                       }
                     
                }
             }
	}

	public void removeStudent(StudentNode studentNode)  {

	    StudentNode p;
            if (checkStudent(studentNode)) {

               for (p = sList; !(p.equals(studentNode)); p = p.getNext());

               if (p == sList) {
                        sList = sList.getNext();
               } else {
                      StudentNode q = sList;
                      while (q.getNext() !=  p) 
                            q = q.getNext();
                            			
                      q.setNext(p.getNext());
                 }
             }
	}

	public boolean checkStudent(StudentNode studentNode)  {
	
		for (StudentNode ptr = sList; ptr != null; ptr = ptr.getNext())
			if (ptr.equals(studentNode))
				return true;
		return false; 
        
	}
	
	public String toString()  {

		String s = "";

                for (StudentNode ptr = sList; ptr != null; ptr = ptr.getNext())
                    s += ptr.toString() + '\n';

 		return s;
	}

}

import java.awt.*;
import java.applet.*;
import java.util.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;

public class LinkedListStudentDBTester extends Applet 
                           implements ItemListener,
				      ActionListener  { 

  LinkedListStudentDB  studentDB;

  TextArea result;
  TextField tfNumber;
  Choice fileURL;
  Label label1,label2;

  String datafile[] = {	"studfile1.html",
			"studfile2.html",
			"studfile3.html",
			"studfile4.html" };

  public void init() {


    result = new TextArea(12,80);
    label1 = new Label("Test Case");
    label2 = new Label("Remove Student");
    tfNumber = new TextField(10);
 

    fileURL = new Choice();

    for (int i = 0; i < datafile.length; i++)
	fileURL.add(datafile[i]);

    add(label1);
    add(fileURL);
    add(label2);
    add(tfNumber);
    add(result);
     
    fileURL.addItemListener(this);
    tfNumber.addActionListener(this);
  }

  public void itemStateChanged(ItemEvent ie) {

    studentDB = new LinkedListStudentDB();

    try {
    	URL url = new URL("http://personal.cityu.edu.hk/~dcywchan/2003dco10103/" +
                           fileURL.getSelectedItem());
	URLConnection data = url.openConnection();
        BufferedReader inFile = new BufferedReader(new InputStreamReader(data.getInputStream()));

        String textLine;
  
        while((textLine = inFile.readLine()) != null) {
 
          StringTokenizer  st = new  StringTokenizer(textLine, "_");

	  studentDB.addStudent(new StudentNode(Integer.parseInt(st.nextToken()),
                                           st.nextToken(),
					   Integer.parseInt(st.nextToken())));
         }

        result.setText("");
        result.setText(studentDB.toString());
        inFile.close();
    } catch(MalformedURLException mue) {}
      catch(IOException ioe) {}
  }

  public void actionPerformed(ActionEvent e) {

     studentDB.removeStudent(new StudentNode(Integer.parseInt(tfNumber.getText())));
     result.setText("");
     result.setText(studentDB.toString());
  }
}