I can't print an array grid with objects and my class? Netbeans w/ Java

Question

I am making a grid with the amounts determined by a scanner. I keep getting an error and I am not sure why. Here is the code for the grid that I am trying to make, I will also include the object and class for the maze/grid below.

public static void mazeSetup() {                                        
    System.out.println("How many rows and columns do you want? I would\n"
                     + "suggest 10 minimum and 20 maximum.");
    boolean mazeselect = true;
    while(mazeselect) {
    maze.columns = sc.nextInt();
    maze.rows = maze.columns;
    if (maze.rows > 30 || maze.rows < 10) {
        System.out.println("Make sure that you make it within 10-30 rows.");
    } else {
        mazeselect = false;
    }
  }
    mazeBuild();
}

public static void mazeBuild() {
    for(int x = 0; x < maze.rows; x++) {
        for(int y = 0; y < maze.columns; y++) {
            maze.maze[x][y]= ".";
            System.out.print(maze.maze[x][y]);
    }
        System.out.println();
}
characterPlacement();

}

I also have the object here:

static Maze maze = new Maze(null,0,0,0,0);

and the class with construtors for the maze/grid.

public class Maze {

    String maze[][];
    int rows;
    int columns;
    int xStart;
    int yStart;

public Maze(String xMaze[][], int xRows, int xColumns, int xxStart, int xyStart) {     
        maze = xMaze;
        rows = xRows;
        columns = xColumns;
        xStart = xxStart;
        yStart = xyStart;
    }
    public String[][] maze() {
        return maze;
    }
    public int rows() {
        return rows;
    }
    public int columns() {
        return columns;
    }
    public int xStart() {
        return xStart;
    }
    public int yStart() {
        return yStart;
    }

}

Any help would be greatly appreciated. Thanks a lot! :D

Note: No errors occur until ran in console.

Answer 1

your String maze[][] is null because of this:

static Maze maze = new Maze(null,0,0,0,0); // notice that null

And you're trying to put values in it upon calling mazeBuild() . You should initialize it or pass an array instead of null . You can do this at the start of mazeBuild()

public static void mazeBuild() {
    maze.maze = new String[maze.rows][maze.columns]; // <-- this one!

    for(int x = 0; x < maze.rows; x++) { // <-- this loop tries to
        for(int y = 0; y < maze.columns; y++) { // put values in your
            maze.maze[x][y]= ".";               // maze.maze (2D String array)
            System.out.print(maze.maze[x][y]);
    }
    System.out.println();
}

You can also do this in exchange to the line of code I've added.

String[][] mazeArray = new String[maze.rows][maze.columns];
maze = new Maze(mazeArray, maze.rows, maze.columns, 0, 0);