来自不带空格的用户的 Java 填充字符矩阵 [duplicate]

问：

我希望能够要求用户填写矩阵。代码有效，但问题是，如果用户不输入带有空格的值，则输出将是错误的。

enter code here
    char [][] matrix = new char[2][2];
    Scanner scanner = new Scanner(System.in);
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 2; j++) {
            matrix[i][j] =scanner.next().charAt(0);
        }
    };

   // the user can enter with space: 
      a b
      c d
   
 // however when the user enters without space the program dont stop and the matrix dont get filled in the right way:
      ab
      cd

// expected output should fill out the matrix with given values from the user without space.