冒号错了，改成英文冒号即可

public class HelloWorld{
    public static void main(String[] args){
        char today='日';
        switch (today){
            case '一':
            case '三':
            case '五':
                System.out.println("吃包子");
                break;
            case'二':
            case'四':
            case'六':
                System.out.println("吃油条");
                break;
            default:
            System.out.println("吃主席套餐");
        }
       }
    }