Lab 3: Building Applets

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Concurrent Programming with Java
Lab Manual, Version 1.0, F. Astha Ekadiyanto, 2002.

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Lab 3: Building Applets - Graphical representation

Modification of existing classes for graphical representation
Defining a MobileStation Class and its related interaction with other objects
Constructing the Applet
Handling MouseEvent
A Challenge Task

Defining a MobileStation Class and its related interaction with other objects

The MobileStation will represent a HandPhone or other mobile devices that will be moved by mouse (See the indended result)

A MobileStation should have:

StationID (something like an IMEI or a Phone Number)
Location (an x,y point)
An Rbs when registered for services

A MobileStation should be able to (behaviour):

Connect to the serving Rbs (when in service/request for service)
Release the currently serving Rbs (when out of service)
Inform the serving Rbs currently used by the MobileStation
Inform its location
And of course a draw() method as a graphical representation of the MobileStation state.

These definitions can be implemented in Java Language as follows :

File name: MobileStation.java

Class Fields :

stationID : The identification String of the Mobile Station
servingRbs : When a MobileStation is in service range of an Rbs, the MobileStation will register the Rbs as the servingRbs.

Class Constructors:

MobileStation(String stationID, x, y) : Initializes all Class Fields using passing arguments.
The MobileStation Class is a subClass of Point Class. Thus, we do not have to define any coordinate fields (x,y) since it has been defined in the Point Class. To access the Point coordinates, we can use the methods getX(), getY(), setX() and setY(). This will save us from defining some accessing methods.

Class Methods:

connectRbs(Rbs) : when an Rbs is assigned to a MobileStation, the MobileStation should be informed to connect to the Rbs.
releaseRbs() : when a MobileStation is out of the Rbs coverage, the MobileStation should be informed to release its connection to the currently connected Rbs.
connectedRbs() : Some object might want to find out which Rbs the MobileStation is currently connected to .
draw(Graphics) : defines the graphical representation of the MobileStation.
A small circle (more like a point) is drawn to represent the MobileStation location.
When the MobileStation is in the service range of an Rbs, it will display a line of sight from the MobileStation to the Rbs.

import java.awt.Point;
import java.awt.Graphics;
import java.awt.Color;    
	
public class MobileStation extends Point  
// To simplify location information, a SuperClass Point is used
// Check Java API Documentation about Point Class definition!
{
    private Rbs servingRbs;
    private String stationID;    
    private static final Color servingColor = new Color(255,0,0);
    private static final Color mobileColor = new Color(0,0,255);    
    
    /**
     * Constructor for objects of class MobileStation
     */
    public MobileStation(String stationID, int x, int y)
    {
        super(x,y);
        this.stationID = stationID;
        servingRbs=null;
    }
   /**
    * Inform the ID of the Base Station
    * @return StringID
    */
    public String getID()
    {
        return stationID;
    }
   /**
    * Perform Rbs service connection
    * @param Rbs The Serving Rbs
    */
    public void connectRbs(Rbs servingRbs)
    {
        this.servingRbs = servingRbs;
    }
   /**
    * Release currently connected Rbs 
    */
    public void releaseRbs()
    {
        servingRbs = null;
    }
   /**
    * Return the currently connected Rbs to the Mobile Station
    */    
    public Rbs connectedRbs()
    {
        return servingRbs;
    }
   /**
    * Draw a graphical representation of the Mobile Station
    * When it is in service range of an Rbs, 
    * a line of sight will be drawn from the Rbs to the Mobile Station
    */
    public void draw(Graphics g)
    {
        Color normalColor = g.getColor();
        int x1 = (int) getX();
        int y1 = (int) getY();        
        // Draw the mobile station representation
        g.setColor(mobileColor);        
        g.fillOval(x1-1,y1-1,3,3); 
        if ( servingRbs != null) {
            int x2 = (int) servingRbs.getCell().getX();            
            int y2 = (int) servingRbs.getCell().getY();
            g.setColor(servingColor);
            g.drawLine(x1,y1,x2,y2);
         }
         g.setColor(normalColor);                   
    }
}

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