I have to use constructors in my assignment so i decided to create two mazes (using arrays) and save them in two separate classes (maze1 and maze2). Then i called the array and save the reference to another array named mazeChoice (Line 23) . After, i try to print out the maze by calling the output method (line 24). However when i does this a nullpointerException error pops up.

Any Ideas? Thanks in advance

import java.io.*;
public class MazeAssignment {
    public final String FINISH = "X ";
    public final String GO = ". ";
    public int MAXCOL = 12;
    public int MAXROW = 8;
    public boolean success = false;
    public static void main (String args[]) throws IOException {
        Maze1 mazeOne = new Maze1();
        String mazeChoice [][]=new String[8][12];
        Maze2 mazeTwo = new Maze2();
        MazeAssignment SA = new MazeAssignment();
        int x, y, userInput;
        System.out.println("Maze One");
        mazeChoice = mazeOne.structure;
        System.out.println();
        System.out.println("Maze Two");
        mazeChoice = mazeTwo.structure;
        System.out.println();
        System.out.println("Press 1 to solve Maze One, or press 2 to solve Maze 2");
        userInput = SA.userInput();
        if(userInput == 1){
            mazeChoice = mazeOne.structure;
            SA.output(mazeChoice);
        }
        else{
            mazeChoice = mazeTwo.structure;
            SA.output(mazeChoice);
        }
        System.out.println("Enter X Coordinate(Points 2 - 6)");
        x = SA.userInput();
        System.out.println("Enter Y Coordinate(Points 2 - 10)");
        y = SA.userInput();
        SA.output(mazeChoice);
        mazeChoice = SA.solveMaze(x, y, mazeChoice);
        mazeChoice = SA.cover(mazeChoice);
        System.out.println();
        SA.output(mazeChoice);
    }
    public void output(String mazeChoice[][]){
        for (int count1 = 0; count1 < 8; count1++){
            for (int count2 = 0; count2 < 12; count2++){
                System.out.print(mazeChoice[count1][count2]);
            }System.out.println();
        }
    }
    public int userInput () throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        return Integer.parseInt(br.readLine());
    }

class Maze1 {
    String structure[][];
    Maze1(){
        String structure [][] = {
                {" ", "1 ", "2 ", "3 ", "4 ", "5 ", "6 ", "7 ", "8 ", "9 ", "10 ", "11 "},
                {"1 ", "B ", "B ", "B ", "B ", "B ", "B ", "B ", "B ", "B ", "B ", "B "},
                {"2 ", "B ", ". ", ". ", ". ", "B ", ". ", "B ", ". ", ". ", ". ", "B "},
                {"3 ", "B ", ". ", "B ", ". ", "B ", ". ", "B ", ". ", "B ", "B ", "B "},
                {"4 ", "B ", ". ", "B ", ". ", ". ", ". ", ". ", ". ", ". ", ". ", "B "},
                {"5 ", "B ", ". ", "B ", "B ", "B ", "B ", ". ", "B ", "B ", ". ", "B "},
                {"6 ", "B ", ". ", "B ", ". ", ". ", ". ", ". ", ". ", "B ", ". ", "B "},
                {"7 ", "B ", "B ", "B ", "B ", "B ", "B ", "B ", "X ", "B ", "B ", "B "},
        };
    }
}
class Maze2{
    String structure[][];
    Maze2(){
        String structure [][] = {
                {" ", "1 ", "2 ", "3 ", "4 ", "5 ", "6 ", "7 ", "8 ", "9 ", "10 ", "11 "},
                {"1 ", "B ", "B ", "B ", "B ", "B ", "B ", "B ", "B ", "B ", "B ", "B "},
                {"2 ", "B ", ". ", "B ", ". ", "B ", ". ", "B ", ". ", ". ", ". ", "B "},
                {"3 ", "B ", ". ", "B ", ". ", "B ", ". ", "B ", ". ", "B ", "B ", "B "},
                {"4 ", "B ", ". ", ". ", ". ", "B ", ". ", ". ", ". ", ". ", ". ", "B "},
                {"5 ", "B ", ". ", "B ", ". ", "B ", ". ", "B ", "B ", "B ", ". ", "B "},
                {"6 ", "B ", ". ", "B ", ". ", ". ", ". ", ". ", ". ", "B ", "X ", "B "},
                {"7 ", "B ", "B ", "B ", "B ", "B ", "B ", "B ", "B ", "B ", "B ", "B "},
        };
    }
}

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