• only one student
• repeated student
• 6 students
• typical class

import java.awt.*;
import java.applet.*;
import java.util.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import student.Student;
import student.StudentDB;

public class StudentDBTester extends Applet 
                           implements ItemListener,
				      ActionListener { 

  StudentDB studentDB;

  TextArea result;
  Button sortButton;

  Choice fileURL;
  Label label1,label2;
  TextField tfNumber;


  String datafile[] = {	"studfile1.html",
			"studfile2.html",
			"studfile3.html",
			"studfile4.html" };
  public void init() {

    sortButton = new Button("Sort by grade");
    result = new TextArea(12,80);
    label1 = new Label("Test Case");
    label2 = new Label("Search by ID");
    tfNumber = new TextField(10);

    fileURL = new Choice();

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

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

  public void itemStateChanged(ItemEvent ie) {

    studentDB = new StudentDB();

    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 Student(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) {

    if (e.getSource().equals(sortButton)) {
       studentDB.sortStudentByMark();
       result.setText("");
       result.setText(studentDB.toString());     
    }
    else if (e.getSource().equals(tfNumber)) {
            Student tempStud = new Student(Integer.parseInt(tfNumber.getText()));
            Student lookUpResult = studentDB.lookUpStudent(tempStud);
            if (lookUpResult != null) {
                result.setText("");
                result.setText(lookUpResult.toString());    
            }
         }
  }
}