enum 사용 연습

Using an enum, implement the getLetterPosition() method, which must return a letter's position. The position of the letter A is 1.

Initialize the wheels field using data from loadWheelNamesFromDB(). Throw an exception if the data is invalid. Hint: if wheels aren't right, then it's not a car! Don't change the signatures.

Make Column implement the Columnable interface. See the Javadocs for a description of its methods. Implement the logic of the Column.getVisibleColumns() method. The Column.configureColumns() method is already implemented. Don't change it. Don't create additional fields.