一个Java的BUG，请大神解答下！！谢谢！！！

public class TetrominoGame {
//测试
public static void main(String[] args) {
//构造T类
TetrominoT t = new TetrominoT(0,4);
printTetrominoGame(t);
//构造J类
TetrominoJ j = new TetrominoJ(0,4);
printTetrominoGame(j);
}
//打印场地
public static void printTetrominoGame(Tetromino tetromino) {
int totalRows = 20;
int totalCols = 10;
Cell[] cells = tetromino.cells;

    for(int row=0;row<totalRows;row++) {
        for(int col=0;col<totalCols;col++) {
            boolean isInCells = false;
            for(int i=0;i<cells.length;i++) {
                if(row == cells[i].row && col == cells[i].col) {
                    System.out.println("*");
                    isInCells = true;
                    break;
                }
            }
        }
        System.out.println();
    }
}

}
class Tetromino {
Cell[] cells;

public Tetromino() {
    cells = new Cell[4];
}
//打印
public void print() {
    String str = "";
    for(int i=0;i<cells.length;i++) {
        str += "(" + cells[i].getCellInfo() + ")";
    }
    System.out.println(str);
}
//下落
public void drop() {
    for(int i=0;i<cells.length;i++) {
        cells[i].row++;
    }
}
//左移
public void leftMove() {
    for(int i=0;i<cells.length;i++) {
        cells[i].col--;
    }
}
//右移
public void rightMove() {
    for(int i=0;i<cells.length;i++) {
        cells[i].col++;
    }
}

}
//T类
class TetrominoT extends Tetromino{

Cell[] cells;
//构造方法
public TetrominoT(int row,int col) {
    super();
    cells = new Cell[4];
    cells[0] = new Cell(row,col);
    cells[1] = new Cell(row,col + 1);
    cells[2] = new Cell(row,col + 2);
    cells[3] = new Cell(row + 1,col);
}

}
//J类
class TetrominoJ extends Tetromino {
Cell[] cells;
//构造方法
public TetrominoJ(int row,int col) {
super();
cells = new Cell[4];
cells[0] = new Cell(row,col);
cells[1] = new Cell(row,col + 1);
cells[2] = new Cell(row,col + 2);
cells[3] = new Cell(row + 1,col);
}

}
//格子
class Cell {
int row;
int col;
public Cell(int row,int col) {
this.row = row;
this.col = col;
}

public String getCellInfo() {
    return row + "," + col;
}

}
这是源代码

这是错误信息
请各位帮我调一调

cells[i].row跟cells[i].col为空，取不出来值

主要是你的printTetrominoGame的第22行有错，仔细看看