Java：使用私有字段进行对象访问

Question

This are my two classes. Eclipse, underlines myGrid[0] inside while-loop and I get a message " The type of the expression must be an array type but it resolved to Grid ". Appreciate any help.

public class Grid {
  private int[][] myGrid;
  private int x, y;

  public Grid(int x, int y) {
    myGrid = new int[y][x];
  }
}

---

import java.util.Scanner;

public class Play {

  private Scanner input = new Scanner(System.in);

  private void setPosition (Grid myGrid) {
    boolean counter = false;

    while (counter == false) {
      System.out.println("Give a position, from 0 to " + myGrid[0].length-1 + " : >");
      x = Integer.parseInt(input.nextLine());
    }
  }
}

Answer 1

You're confusing the Grid class with its myGrid field. They are completely different. Just because you give your Grid parameter the same name as its field, it's not the same thing. myGrid is a Grid variable pure and simple, and not an array.

Here:

private void setPosition (Grid myGrid) {

myGrid is a Grid variable and is not an array and cannot be treated as such. If this were my code, I'd give the Grid class a getColumnCount() method

public class Grid {
    private int[][] myGrid;
    private int x, y;

    public Grid(int x, int y) {
        myGrid = new int[y][x];
    }

    public int getRowCount() {
        return myGrid.length;
    }

    public int getColumnCount() {
        return myGrid[0].length;
    }
}

and call it:

private void setPosition (Grid myGrid) {
    boolean counter = false;

    while (!counter) {
        System.out.println("Give a position, from 0 to " + (myGrid.getColumnCount() - 1) + " : >");
        x = Integer.parseInt(input.nextLine());
    }
}