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Java enum

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Started by Shakedown February 13, 2008 10:26 PM

15 comments, last by pinacolada 16 years, 2 months ago

Shakedown

231

Author

February 13, 2008 10:26 PM

I don't understand what the problem is here with my use of enum. GAME_CONSTANTS.java


public interface GAME_CONSTANTS {
	
	// Directions Ships travel in
	enum Direction {NORTH, SOUTH, EAST, WEST};

Ship.java


// Movement methods
	public void move(Direction dir){
		switch(dir){
			case NORTH:
				if((coordinate.getY() - speed) >= 0)
					coordinate.moveY(-speed);
				break;
			case SOUTH:
				if((coordinate.getY() + speed + sprite.getHeight()) <= BACKGROUND_HEIGHT)
					coordinate.moveY(speed);
				break;
			case EAST:
				if((coordinate.getX() + speed + sprite.getWidth()) <= BACKGROUND_WIDTH)
					coordinate.moveX(speed);
				break;
			case WEST:
				if((coordinate.getX() - speed) >= 0)
					coordinate.moveX(-speed);
				break;
		}
	}

Game.java


// Read keyboard input
			if(leftPressed) 	playerShip.move(WEST);
			if(rightPressed)	playerShip.move(EAST);
			if(upPressed)		playerShip.move(NORTH);
			if(downPressed)		playerShip.move(SOUTH);

The error reads: WEST cannot be resolved Yes all the classes implement the GAME_CONSTANTS interface.

Destination: Chaos![My WebLog :: Programming | Computing | Fantasy | Metal]

DevFred

840

February 14, 2008 08:47 AM

Quote:Original post by Shakedown
Yes all the classes implement the GAME_CONSTANTS interface.

That's just horrible. Does saying "A ship is a game constants" make sense to you?

Antheus

2,410

February 14, 2008 08:58 AM

Quote:Original post by DevFred
Quote:Original post by Shakedown
Yes all the classes implement the GAME_CONSTANTS interface.

That's just horrible. Does saying "A ship is a game constants" make sense to you?

That's common idiom for Java constants due to lack of namespaces. It saves typing while retaining correct values.

It is not a design, just a coding practice.

smitty1276

560

February 14, 2008 09:13 AM

Quote:Original post by Antheus
That's common idiom for Java constants due to lack of namespaces. It saves typing while retaining correct values.

It's still hideous... at LEAST call the interfact GameConstantsConsumer, or GameObject or something. There should be some good way to organize your classes so that classes implement the interfaces they actually need and get the constants at the same time.

Furthermore, such abuses of OO constructs are even less excusable now, since static imports have been part of the language for some time.

Antheus

2,410

February 14, 2008 09:17 AM

Quote:Original post by smitty1276
Quote:Original post by Antheus
That's common idiom for Java constants due to lack of namespaces. It saves typing while retaining correct values.

It's still hideous... at LEAST call the interfact GameConstantsConsumer, or GameObject or something. There should be some good way to organize your classes so that classes implement the interfaces they actually need and get the constants at the same time.

Furthermore, such abuses of OO constructs are even less excusable now, since static imports have been part of the language for some time.

Yes, sadly Java community has too much momentum.

Anyway, back to real problem:

if(leftPressed) 	playerShip.move(Direction.WEST);if(rightPressed)	playerShip.move(Direction.EAST);if(upPressed)		playerShip.move(Direction.NORTH);if(downPressed)		playerShip.move(Direction.SOUTH);

Ironically, your problem stems exactly from the above abuse of interfaces to save typing, something which isn't needed since enum keyword was added.

greggles

348

February 14, 2008 09:47 AM

Instead of inheriting from an interface, you should probably use static imports.

Greggles

Shakedown

231

Author

February 14, 2008 10:54 AM

Quote:Original post by Antheus
Anyway, back to real problem:

if(leftPressed) playerShip.move(Direction.WEST);
if(rightPressed) playerShip.move(Direction.EAST);
if(upPressed) playerShip.move(Direction.NORTH);
if(downPressed) playerShip.move(Direction.SOUTH);

Thank you. I thought I tried this, but it works fine now. I looked online in several different places for uses of enums, but somehow none of them used them across multiple files.

Quote:Original post by greggles
Instead of inheriting from an interface, you should probably use static imports.

Greggles

Is this a common convention to access important globals all throughout your program, as opposed to implementing a constants interface?

Destination: Chaos![My WebLog :: Programming | Computing | Fantasy | Metal]

DevFred

840

February 14, 2008 12:58 PM

A common convention is to avoid globals like the pest.

Sleep

134

February 14, 2008 01:09 PM

I declare my constants in a static class with its variables public but final. If things get complicated, get-methods can return related stuff that is just a few conversions away. Hence, I can access it from everywhere without passing around anything.

I have never talked to anyone about this, though. There might be reasons against it that I don't know ...