CODEWITHSUNDEEP
java
Greg Smith
Greg Smith

Reputation: 67

ArrayIndexOutOfBoundsException for unknown reason

I'm writing a program that creates a maze as a 2d array. I've run into a hiccup, and that is ArrayIndexOutOfBoundsException. It is pointing to maze[0][0] = "S" in the drawMaze method. I'm scratching my head at this, I have no idea why it's throwing an error.

import java.util.Random;

public class LA2_MazeSolver {

private int rows;
private int cols;
private String[][] maze = new String[rows][cols];

LA2_MazeInput mi = new LA2_MazeInput();

public void setNumRows(int numRows) {

    this.rows = numRows;

}

public void setNumCols(int numCols) {

    this.cols = numCols;

}

public int getNumRows() {

    return this.rows;

}

public int getNumCols() {

    return this.cols;

}

public void drawMaze() {

    Random r = new Random();

    maze[0][0] = "S";
    maze[rows - 1][cols - 1] = "D";
    int limit = ((rows * cols) / 3);

    for (int i = r.nextInt(limit) + 1; i < limit; i++) {

        maze[r.nextInt(rows) - 1][r.nextInt(cols) - 1] = "#";

    }

    for (int i = 0; i < maze.length; i++) {
        for (int c = 0; c < maze[0].length; c++) {

            if (!(maze[i][c].matches("#")) && !(maze[i][c].matches("S")) && !(maze[i][c].matches("D"))) {

                maze[i][c] = Integer.toString(r.nextInt(100) + 1);

            }

        }
    }

}

public void printMaze() {

}

/*public boolean isSolvable() {

    return solveMazeRecursively(this.rows, this.cols);

}

private boolean solveMazeRecursively(int row, int col) {

}*/

public void printResult() {

}
}

Upvotes: 1

Views: 86

Answers (2)

John Dengis
John Dengis

Reputation: 192

In Java, you can't make a definition like private String[][] maze = new String[rows][cols]; outside of the constructor. At that point in the the code, the value for row and col have not been defined and so something like private String[][] maze = new String[rows][cols]; won't have well defined behaviour (row and col may in fact be 0, who knows).

Try instead something like this:

    private int row;
    private int col;
    private String[][] maze;

    public LA2_MazeSolver(int row, int col) {
        this.row = row;
        this.col = col;
        maze = new String[row][col]
    }

Now when you create a LA2_MazerSolver object, you will dynamically create an array of the correct size to use (for example solver = new LA2_MazeSolver(row, col)).

Upvotes: 0

VHS
VHS

Reputation: 10174

It's simple. You are getting the Array Index Out of Bound exception because you are exceeding the array boundaries.

I've run into a hiccup, and that is ArrayIndexOutOfBoundsException. It is pointing to "maze[0][0] = "S";"

You have declared maze in the following block

private int rows;
private int cols;
private String[][] maze = new String[rows][cols];

Note that you are specifying a size of 'rows' and 'cols' for 'maze'. But these values are 0 and 0 respectively. See that you are not giving a value to rows and cols at the time of initialization. So the default value of int primitives declared as class members is 0.

To fix this problem, initialize rows and cols to a value greater than 0.

Upvotes: 2

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