二维整数数组不接受我提供的尺寸

Question

This is the code that is in my GridGenerator class. The purpose is to create multiple rectangular rooms that can eventually be joined together into a map.

int xRange, yRange;

//constructor
public GridGenerator(int xInput, int yInput) {
    xRange = xInput;
    yRange = yInput;
}

int[][] grid = new int[yRange][xRange];
//the first number indicates the number of rows, the second number indicates the number of columns
//positions dictated with the origin at the upper-left corner and positive axes to bottom and left

void getPosition(int x, int y) {
    int position = grid[y][x]; //ArrayIndexOutOfBoundsException here
    System.out.println(position);
}

This is the code that is in my MapperMain class. The purpose is to join GridGenerator instances into a multi-room map. I'm also using it for debugging and scaffolding purposes for now.

public static void main(String[] args) {

    GridGenerator physicalLayer1 = new GridGenerator(10,15);

    physicalLayer1.getPosition(0, 0); //ArrayIndexOutOfBoundsException here

}

I'm getting an ArrayIndexOutOfBoundsException error. At some point, xRange is assigned a value of 10 and yRange is assigned a value of 15. However, when I attempt to use xRange and yRange as the parameters for grid , Java has some problem with that and I'm not sure why. If I assign values to xRange and yRange in the GridGenerator class, there doesn't seem to be a problem. When I use the constructor in the MapperMain class, I get this error.

Answer 1

This line

grid = new int[yRange][xRange];

should be in the constructor, since in your code sample grid has never been initialized with proper values of yRange and xRange .

So - your class should look something like this:

public class GridGenerator {
     private int xRange, yRange;
     private int[][] grid;

     //constructor
     public GridGenerator(int xInput, int yInput) {
         xRange = xInput;
         yRange = yInput;
         grid = new int[yRange][xRange]; 
     }

     ...
}

Answer 2

The problem is this line:

int[][] grid = new int[yRange][xRange];

despite being coded after the constructor, is executed before the constructor executes, and when the line executes the size variables have their default initialization values of 0 .

The reason it executes before the constructor is due to the initialization order: (among other things) All instance variables are initialized, in the order coded, before the constructor executes.

To fix the problem, change your code to:

// remove variables yRange and xRange, unless you need them for some other reason
int[][] grid;

public GridGenerator(int yRange, int xRange) {
    grid = new int[xRange][yRange];
}

Answer 3

int[][] grid = new int[yRange][xRange]; 

您必须在数组范围内给出一些固定值，如果要查找动态数组，请使用数组列表