0 
public class someClass{
public String[][] board = new String[7][7];

public someClass(){
    for (int i = 0; i < board.length; i++) {
        for (int j = 0; j < board[i].length; j++) {
            board[i][j] = " ";
        }
    }
}

I have this in a class I am using, I an struggling to find a way to search through the array and see if the cells left, right, above or below of a particular cell are empty or filled.

I.E board[4][2] - how would I look through the array to see if position [4][1], [4][3], [3][2] and [5][2] are empty or have an element inside of them?

EDIT: I have tries to use nested for loops to look through the array and subtract 1 from the indexes in the loop, however that provides nothing.

Improve this question
9
  • 2
    have you tried to do it ? Commented Mar 17, 2016 at 14:03
  • 2
    Add or subtract one from the first or second index. Commented Mar 17, 2016 at 14:04
  • 2
    simple math will do it. Commented Mar 17, 2016 at 14:04
  • Yes, should have mentioned sorry. I initially tried to to nested for loops and looking ai i-1 and j-1 etc, however that displayed nothing. POST EDITED Commented Mar 17, 2016 at 14:04
  • Could you post those nested for loops? Commented Mar 17, 2016 at 14:07

2 Answers 2

Reset to default
1 
Above: [i][j - 1]
Below: [i][j + 1]
Before: [i - 1][j]
After: [i + 1][j]

Just make sure to check for out of bounds first. Then:

private boolean isInBounds(int i, int j) {
    return (board.length > 0 && i >= 0 && i < board.length && j >= 0 && j < board[i].length);
}

private boolean isAboveEmpty(int i, int j) { // This might be a little verbose...
    int newJ = j - 1;
    if(isInBounds(i, newJ)) 
        return board[i][newJ].equals(" "); //Above cell is empty
    return true; // out of bounds cells are always empty (or are they?)
}

Then repeat for other directions. Make board private too, and let user use a set method to set the cells, so you can do your check first.

public class Board {
    private String[][] board = new String[7][7];
    ...
    public void set(int i, int j, String value) {
        if(isInBounds(i, j) && isAboveEmpty(i, j) && isBelowEmpty(i, j) && isBeforeEmpty(i, j) && isAfterEmpty(i, j)) {
            board[i,j] = value;
        }
    }
}
Improve this answer
Sign up to request clarification or add additional context in comments.

3 Comments

This makes sense, thank you for your input. I now understand how to do this and how it works :)
how would I go about doing the opposite of this. So if I have one cell and that becomes surrounded on four sides by other elements then it displays a message?
After you do board[i,j] = value; call a method checkNeighbours(int i, int j) that checks for each of the neighbour cells if they are now surrounded. (isSurrounded(int i, int j) could be another method).
1 
public class someClass{

    public String[][] board = new String[7][7];

    public List<Coordinates> findAdjacentCells(final String[][] board, final int x, final int y){
        List<Coordinates> result = new ArrayList<Coordinates>();

        if(x >= 1 && y >= 1) {
            if(y + 1 < board[x].length)
                result.put(new Coordinates(x, y + 1));
            if(y - 1 >= 0)
                result.put(new Coordinates(x, y -1));
            if(x + 1 < board.length)
                result.put(new Coordinates(x+1, y));
            if(x -1 >= 0)
                result.put(new Coordinates(x-1, y));
        }

        return result;
    }
        // Keep track of coordinates
        public class Coordinates {
            int positionX;

            int positionY;

            public Coordinates(int positionX, int positionY) {
                super();
                this.positionX = positionX;
                this.positionY = positionY;
        }

        public final int getPositionX() {
            return positionX;
        }

        public final int getPositionY() {
            return positionY;
        }
    }
}

You can do something like the above. I did not know if your board has position 0. Obviously the array does. So you might have to change some of the conditionals around.

Edit: You edited your question and added more code, this might not be relevant anymore.

Improve this answer

4 Comments

thanks for the input I do see what you're doing there for the most part, the list of ifs gives a "method put(String) is undefined for the type List<Board.Coordinates>
I fixed it, I meant to be creating objects instead of adding the array. Alternatively instead of using the Coordinates class you can make the List be a List<String[][]> and then do a result.put(board[x][y + 1]). It depends if you need the positions or what's inside the position. Your edit says you are doing a comparison so maybe you just need the values not the coordinates.
But if x or y = 0, you get an empty list, so you can't get the adjacent cells of first row/collumn cells.
@JornVernee you are right. We don't know how @Topher wants to handle position 0. I suspect if it's a game board of some sort the corner is 1,1. However if it's 0,0 then the first conditional check x >= 1 will have to be changed to x >= 0.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.