HAS-A relationship?

[Akhash Ramamurthy]

Whats the relationship between the LIGHT and REMOTE class?

  

public class Light()
{

public light(){}

private void switchOn()
{
System.out.println("ON");
}

private void switchOFF()
{
System.out.println("OFF");
}
}



==================

public class Remote()
{

 private Light light = null;
 private Boolean isOn = false;   // default is OFF

public remote (Light light)
{
this.light = light;
}

public void toggleButtonPressed()
{
if (! isOn)
{
light.switchOn();
}else {
light.switchOff();
}
}

  

Whats the relationship between the LIGHT and REMOTE class? (interms of association or composition)

I dont think Remote Has-A a light is valid relationship.... But in the real-world Light Has-A Remote seems to be correct for me.... Whats your opinion?

[Bear Bibeault]

Please do not post the same question more than once.

[Campbell Ritchie]

Bear Bibeault wrote:Please do not post the same question more than once.

Agree. Since the other posting was on somebody else's thread, that is regarded as hi-jacking the old thread. I have obscured the other post so you won't get any replies there.

[Akhash Ramamurthy]

Sorry for posting the question twice. Thought it might go unnoticed if my question is under a old thread... So created a new thread.
Anyways can I get an answer for my question ?

[Campbell Ritchie]

Apology accepted
It was better to create a new thread for a new question.

I think you are correct: remote has-a light. Whether that has anything to do with the real world is not important. Your code creates a situation where a remote has a light, and if the real world is different, well that's the real world's problem .

[Ninad Kuchekar]

Hi Akhash,

What you are thinking is absolutely correct, and it should be that way and it can.

I don't think switchOn() or switchOff() is the behavior of light, it is the function of a remote. The light simply responds to these commands. You could think on those lines...

Campbell Ritchie wrote: ..and if the real world is different, well that's the real world's problem.

Javattidude!

[Abimaran Kugathasan]

Akhash Ramamurthy wrote:

  
public class remote()
{
....
..

There is a syntax error in the coding. Nobody noticed?

[Ninad Kuchekar]

Abimaran Kugathasan wrote: There is a syntax error in the coding. Nobody noticed?

Whoops!!...Think I got too excited about leaving for home...

[Shanky Sohar]

donot compare this code with a real world..
you can even make a class Animal which has all the birds

class Peacock{
}
class Elephant{
private Peacock peak=null
....
....
...
...

}

but i can see that your code has class remote which call light class methods to check whether the button is pressed or not.

[Shanky Sohar]

Abimaran Kugathasan wrote:

Akhash Ramamurthy wrote:

  
public class remote()
{
....
..

There is a syntax error in the coding. Nobody noticed?

Good Catch..Great..

[Akhash Ramamurthy]

Ninad Kuchekar wrote:

Abimaran Kugathasan wrote: There is a syntax error in the coding. Nobody noticed?

Whoops!!...Think I got too excited about leaving for home...

Thanks. I have got it rectified.

[Akhash Ramamurthy]

Ninad Kuchekar wrote:Hi Akhash,

What you are thinking is absolutely correct, and it should be that way and it can.

I don't think switchOn() or switchOff() is the behavior of light, it is the function of a remote. The light simply responds to these commands. You could think on those lines...

Campbell Ritchie wrote: ..and if the real world is different, well that's the real world's problem.

Javattidude!

I actually tried to create a loosely coupled design. That made me think ON and OFF is something that the light should do and not the remote... Later if the requirement changes and if I introduce a dimmer behavior for the light I can still use the same toggleSwitchPressed() function in the Remote to dim or brighten the light...

[Akhash Ramamurthy]

My actual problem is how to relate these two classes in a UML diagram? Whats the relationship they share ?

[Gary Ba]

UML:
Remote -> Light

has-a/association relationship can be shown on UML diagram as an arrow.

Gary

[Akhash Ramamurthy]

Gary Ba wrote:UML:
Remote -> Light

has-a/association relationship can be shown on UML diagram as an arrow.

Gary

Thanks Gary.
How you say Remote --> Light (Has-A) relation?
Can you please explain me.... I have an interesting scenario based on your answer.

[Ninad Kuchekar]

So what Gary has said above is perfect. If you are still fighting for a real world solution and to make it loosely coupled create an Interface, say Transponder.

So something like:

 interface Transponder{
       public void switchOn();
       public void switchOff();
}   

Now,

  class Light implements Transponder{
...//implemented methods from Transponder
}  

Now use this Interface reference in your class Remote. You could also add some more Transponders by implementing this interface. Now your Remote "has-a" Transponder.

There is much more you could do to the above code to make it close to real world. You could add another abstract level between the interface and your class. But this one is simple enough.

[Ninad Kuchekar]

I am not an avid UML user, but isn't "has-a" relationship denoted like this...
Remote<--Light...?

[Akhash Ramamurthy]

Sorry if I am taking this very deep..

  
public class Elevator ()
{
Button firstFloorbutton      = ButtonFactory.getButtonInstance(this, 1);
Button secondFloorbutton  = ButtonFactory.getButtonInstance(this, 2);
Button thirdFloorbutton     = ButtonFactory.getButtonInstance(this, 3);
Button fourthFloorbutton   = ButtonFactory.getButtonInstance(this, 4);

Fan fan1 = FanFactory.getFanInstance(this);

Light light1 = LightFactory.getInstance(this);

private void goUp()
{
.....
}

private void goDown()
{
......
}

.............   

}

============================

public class Button()
{

Elevator E;
int floor;

public button (Elevator E, int floor )
{
this.E = E;
this.floor = floor;
}

public void buttonPressed()
{

//logic to determine which floor the elevator is currently at and determine whether to go up or down to reach "this.floor"

E.goUp();  // if need to go up

else

E.goDown()   // if need to go down
}
}


==========================


public class ButtonFactory()
{

public Button getButtonInstance(Elevator E, int floor)
{
Button b =new Button(E, floor);
return b;
}
}

==================

public class FanFactory(){ .................}

=====================

public class LightFactory() { ........... }


==========================

Whats the relationship between the Elevator class and the Button class ?
I kind of confused since Elevator has Button members and vice versa....

I didnt use a IDE to type my code.... so if any typos please dont pounce on me... :-)

[Gary Ba]

I am not an avid UML user, but isn't "has-a" relationship denoted like this...
Remote<--Light...?

The arrow should point the other way around. As far as straight line and broken arrow, I know straight line has stronger relationship than dashes. (maybe this is a C++ thing).

Gary

[Akhash Ramamurthy]

Gary,

Any suggestions for my question ?

[Gary Ba]

Whats the relationship between the Elevator class and the Button class ?

It is called Aggregation. Read up on those keyword so you can get a better grasp out of it.
I think it is denoted as

Elevator 1 -> * Buttons

Garry

[Akhash Ramamurthy]

Thanks Gary. Thanks everyone for your replies...