Java - 错误：找不到符号 - 开关/大小写

Question

public static void main(String[] args) {

    System.out.println("Bitte geben Sie einen Betrag und den Buchstaben der gewunschten Wahrung ein.");

    try {
        Scanner input = new Scanner(System.in);

        double betrag = input.nextInt();
        String wahrung = input.next();     
        double result = 0;

        switch(wahrung.charAt(0)) {
            case d:
                result = betrag * 1.18;
                System.out.println(result);
                break;
            case p:
                result = betrag * 0.88;
                System.out.println(result);
                break;
            case f:
                result = betrag * 0.88;
                System.out.println(result);
                break;
        }
    } catch (Exception e) {
        System.out.println("Bitte geben Sie eine Zahl ein.");
    }
}

当我尝试编译它时，它说：

Rechner.java:18: error: cannot find symbol
                case d:
                     ^
  symbol:   variable d
  location: class Rechner
Rechner.java:22: error: cannot find symbol
                case p:
                     ^
  symbol:   variable p
  location: class Rechner
Rechner.java:26: error: cannot find symbol
                case f:
                     ^
  symbol:   variable f
  location: class Rechner

Answer 1

您使用select seq_num, max(trim(id)) keep (dense_rank first order by trim(id)) as first_id, max(trim(name)) keep (dense_rank first order by trim(id)) as first_name from subject group by seq_num order by seq_num asc; 切换，因此每个案例也应该是char值。

尝试

char