如何使用单元的toString()方法为单元的2D数组创建toString()方法？

// 单元类
class Cell {
    private int value;
    private int row;
    private int column;

    public Cell(int value, int row, int column) {
        this.value = value;
        this.row = row;
        this.column = column;
    }

    public String toString() {
        return "Cell [value=" + value + ", row=" + row + ", column=" + column + "]";
    }
}

// 2D数组类
class Array2D {
    private int rows;
    private int columns;
    private Cell[][] cells;

    public Array2D(int rows, int columns) {
        this.rows = rows;
        this.columns = columns;
        this.cells = new Cell[rows][columns];
    }

    public void setCell(int row, int column, Cell cell) {
        cells[row][column] = cell;
    }

    public String toString() {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < columns; j++) {
                sb.append(cells[i][j].toString());
                sb.append(" ");
            }
            sb.append("\n");
        }
        return sb.toString();
    }
}

// 测试代码
public class Main {
    public static void main(String[] args) {
        Array2D array = new Array2D(3, 3);
        array.setCell(0, 0, new Cell(1, 0, 0));
        array.setCell(0, 1, new Cell(2, 0, 1));
        array.setCell(0, 2, new Cell(3, 0, 2));
        array.setCell(1, 0, new Cell(4, 1, 0));
        array.setCell(1, 1, new Cell(5, 1, 1));
        array.setCell(1, 2, new Cell(6, 1, 2));
        array.setCell(2, 0, new Cell(7, 2, 0));
        array.setCell(2, 1, new Cell(8, 2, 1));
        array.setCell(2, 2, new Cell(9, 2, 2));

        System.out.println(array.toString());
    }
}