Exercise

gistfile1.md

The light show !

You are given the task to create the Java classes corresponding to light bulbs (of different characteristics) that can be individually plugged-in on one of the 4 sockets of a control panel allowing the light on or off at will.

The produced code must allow executing the "script" as follows:

static public void main(String[] args) {
    // Technicians are working hard to mount this...
    LightBulb a1 = new LightBulb("yellow");
    LightBulb a3 = new LightBulb("red");
    ControlPanel pdc = new ControlPanel();
    pdc.display();
    pdc.plugInLightBulb(a1, 1);
    pdc.plugInLightBulb(a3, 3);
    pdc.display();

    // The mad lighting designer starts his show !
    for (int i = 0; i < 10; i++) {
        System.out.println("Loop: " + i);
        pdc.display();
        pdc.turnOnLightBulb(1);
        pdc.turnOnLightBulb(2);
        pdc.display();
        pdc.turnOffLightBulb(1);
        pdc.turnOffLightBulb(2);
    }
    
    // The show was crazy !
}

We will make sure that the light bulbs burn-out after they were lit 7 times.

Tasks

• Write the code for the classes LightBulb and ControlPanel in Java.
• Write a class EternalLightBulb for light bulbs that never burn-out. Use this new light bulb type with the panel. You cannot modify the ControlPanel class.
• Identify and explain the conception/coding errors induced by the fact of not having thought of all kinds of bulbs from the start.