Using an array of Strings to create a 2D (map) array in Java

Question

How would it be possible to create a 2D array of characters in Java? I've researching this as applicable to my goal of a map you can move a character around on, though have not found anything helpful. I have done this (with a little help) in C++ before, though don't know how to in Java.

For the C++ version, I started with a 1D array of strings:

    "#######.#.~~~####.##.......~~~..##.~~....H....######..#######",
    "#####..T.#~~~..##.H......~~~...#..T.~~.........######.###....",
    "######..~~~~#######...#..~~~.........~~~.##.###..#####.###...",
    "...###..~~~.######...##H.~~~.@........~~.#.####...##.H.###...",
    ".#####..~~.~~###C.....#..~~~.....#...~~~..###..#....##....#..",
    "######....~~~.~.##....#..~~~.....#....~~~.#######C...........",
    "#######.H..~.~~~~#....#..~~~.....###...~~~.##########........",
    "########.H...~~~~~.....~~~......H..##....~~~.H######...T...##",

(You are the @ Symbol) And then was able to break each string up into separate characters with 2 nested for loops that broke it into what was basically a 2D array that you could move your character around in.

Is this a good way of doing it, if so how? (I've spent 10 hours now attempting to get a basic version to work). Is there a better way of doing this? I would like to create a very complex game later on with a map like this, but need help coming up with how.

You would need nested for loops going through each line of that string and then putting every `.charAt(index)` into a position in the array. Remember 2D arrays are `array[rows][cols] = string.charAt(x)` — 3kings, Oct 13 '15 at 02:02

score 1 · Answer 1 · answered Oct 13 '15 at 02:09

You can create a 2D array in Java by doing

char[][] arr = new char[number of rows][number of columns];

For example,

char[][] arr = new char[2][3];

would create an array that is 2 rows tall and 3 columns wide. Therefore, you could have your character move up and down the grid by changing the row, and have it move left and right by changing the column.

score 1 · Answer 2 · edited May 23 '17 at 11:58

The answer for this question is exactly what you want but with integers.

char[][] multi = new char[number of lines][number of columns];

But I really recommend you use some solution using Objects instead. Since you are using Java.

I don't know your project but I imagine that is a tile based 2D game. You could have a Tile class that have the position information and all properties of a tile.

Another approaches can be used thinking in scalability and performance.

Developer Marius Žilėnas · Accepted Answer · 2015-10-14T04:34:25.677

Well do you need 2D array for your String? Why not store a String like "ABCDEFGHI" and access it as if it was 3x3 2D array?

Map x,y "coordinates" to index.

public class Char2DDemo
{
    public static int ROWS = 3;
    public static int COLS = 3;

    public static class Char2D
    {
        private StringBuilder sb = null;
        private int ROWS;
        private int COLS;

        public Char2D(String str, int rows, int cols)
        {
            this.sb = new StringBuilder(str);
            this.ROWS = rows;
            this.COLS = cols;
        }

        public StringBuilder getSb()
        {
            return sb;
        }

        public int getRowCount()
        {
            return ROWS;
        }

        public int getColCount()
        {
            return COLS;
        }

        public int xy2idx(int x, int y)
        {
            int idx = y * getRowCount() + x;
            return idx;
        }

        public int idx2x(int idx)
        {
            int x = idx % getRowCount();
            return x;
        }

        public int idx2y(int idx)
        {
            int y = (idx - idx2x(idx)) / getRowCount();
            return y;
        }

        public Character getCh(int x, int y)
        {
            return getSb().charAt(xy2idx(x, y));
        }

        public void setCh(Character ch, int x, int y)
        {
            getSb().setCharAt(xy2idx(x, y), ch);
        }
    }

    public static void main(String[] args) throws java.lang.Exception
    {
        String test = "ABC"
                    + "DEF"
                    + "GHI";

        Char2D c2d = new Char2D(test, 3, 3);

        System.out.println("Before " + c2d.getSb());
        System.out.println("at [2][2] " + c2d.getCh(2, 2));
        c2d.setCh('J', 0, 0);
        c2d.setCh('K', 2, 2);
        c2d.setCh('M', 1, 1);        
        System.out.println("After " + c2d.getSb());
        System.out.println("at [1][0] " + c2d.getCh(1, 0));
    }
}

Output:

Before ABCDEFGHI
at [2][2] I
After JBCDMFGHK
at [1][0] B

So I've been reading this approach, and just want to clarify how it handles the array. So it is technically just a 2D array? How then does it seem to take output from a 2D array? Thank you for the help — Jeffrey Cordero, Oct 14 '15 at 14:24
You can think of String as an array of Characters. It's just some specific array. :) Each index is from range [0..n] where n is the number of characters in that String. Specific index 0<=i — Developer Marius Žilėnas, Oct 14 '15 at 15:27
Oh ok, that makes sense, now I can see how they are accessed, thank you for the help! — Jeffrey Cordero, Oct 15 '15 at 18:21

Using an array of Strings to create a 2D (map) array in Java

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