2d array problem

[Daniel Ungerfält]

Hi!
Im trying to make a little game where you have to guess a position in a 2d array.
If you guess right the program just congrats you and brakes. Else its suppose to show you with a "*" where the missed "shot" hits the array but there´s my problem.

public static void main(String[] args) {

		Scanner s = new Scanner(System.in);
		char[][] spel = new char[4][4];

		int a = (int) (Math.random() * 4) + 1;
		int b = (int) (Math.random() * 4) + 1;

		System.out.println("Gissa position i y och x");

		int x = s.nextInt();
		int y = s.nextInt();

		spel[x][y] = '*';

		int j = 1;

		if (x == a && y == b)
			System.out.println("Congrats!");
		else {
			System.out.println(" |1|2|3|4|");
			for (int row = 0; row < spel.length; row++) {

				System.out.print(j + "|");
				j++;
				for (int col = 0; col < spel[row].length; col++) {
					spel[row][col] = ' ';

					System.out.print(spel[x][y]);
				}
                                        System.out.print(spel[x][y]);
				System.out.println();

			}
		}

	}

No mather what I do i cant get the "shots" in the right position or to show upp at all.

RESULT:

Guess position in x and y:
2
3
|1|2|3|4|
1|*
2|*
3|
4|

[Dave Tolls]

System.out.print(spel[x][y]);

Your two for loops use row and col for the array entries, but you are printing x and y.

That's the first thing that leapt out at me.

[Campbell Ritchie]

There ain't no such thing as a 2D array. What you have is an array of arrays.
You are probably using random wrongly. Why +1?
Don't believe what it says in the Java® Tutorials about Math#random being easy to use. Have a look at this thread where there is lots of discussion.

[Campbell Ritchie]

You need to take the logic of that game apart and break it into small parts. Start by getting out of the main method.

[Daniel Ungerfält]

Campbell Ritchie:

What do you mean by there´s no 2d array? Is my teacher fooling me ? ;-)

I use +1 in the math.random cause I want to generate from 1-4 not 0-3.

I know how to fill a array[][] with random numbers I just dont know how to display that*" at the position (x,y) i give it.

If my guess is x: 2 and y: 4 I would like it to show up like:

|1|2|3|4|
1|
2|
3|
4| *

[Daniel Ungerfält]

Got it working now I think:

public class Spel {

	public static void main(String[] args) {

		int x = (int) (Math.random() * 4);
		int y = (int) (Math.random() * 4);

		String[][] spel = new String[4][4];

		
		for (int i = 0; i < spel.length; i++) {

			for (int j = 0; j < spel[i].length; j++) {

				spel[i][j] = " ";
				spel[x][y] = "*";
				System.out.print(spel[i][j]);
			}
			System.out.println();
		}
	}

}

Seems like the "*" appears on the right spot now.

[fred rosenberger]

java does not have true 2-d arrays.

A true 2-d array would only hold one kind of thing. You believe that your "spel" array holds strings, but it doesn't. It holds arrays. Those arrays hold strings.

Think of java 2-d arrays like a shipping crate that holds egg cartons. Those cartons then hold eggs. The egg cartons do not all have to be the same size.

Whereas a true 2-d array would be a big rectangle that holds eggs in each spot.

[Liutauras Vilda]

fred rosenberger wrote:Think of java 2-d arrays like a shipping crate that holds egg cartons. Those cartons then hold eggs. The egg cartons do not all have to be the same size.

I like that expressive rich explanation. I'm sure it will stuck to my mind for future references

[Piet Souris]

fred rosenberger wrote:java does not have true 2-d arrays.

A true 2-d array would only hold one kind of thing. You believe that your "spel" array holds strings, but it doesn't. It holds arrays. Those arrays hold strings.

Think of java 2-d arrays like a shipping crate that holds egg cartons. Those cartons then hold eggs. The egg cartons do not all have to be the same size.

Whereas a true 2-d array would be a big rectangle that holds eggs in each spot.

I agree!

In the first case, one would retrieve an egg with: Egg egg = eggs[2][3].
In the second case, however, one would retrieve that egg with: Egg egg = eggs[2][3].

So it is indeed obvious that the first one is not a genuine 2d array, while the second one is.

Greetz,
Piet

[Campbell Ritchie]

Anyway, is that all the game does? Asks you to guess one out of sixteen squares?
Please write down what you think the logic for printing the square would be.