Question

在我的程序中，我允许用户在Scanner中为书店输入信息，并用它来计算。我遇到麻烦的部分是当用户输入图书的费用时，程序崩溃，因为它没有占用“$”，因为成本是双倍的。我想也许我可以抛出异常或什么？或者可能将成本转换为搜索“$”的字符串，然后将成本转回为双倍，因为计算需要它。有什么想法吗？

到目前为止我所拥有的：

public static final String SENTINEL = "N"; // for sentinel

public static void main(String[]args){
    Scanner input = new Scanner(System.in); // initializing Scanner
    userInput(input);
}

      public static void userInput(Scanner input){

    // Initializing variables
    System.out.print("Do you want to add a book order? (Enter Y for yes/ N for no): ");
        String userInput = input.next();
    String code = "";
    double cost = 0.0; // this is the variable im talking about
    int numBooks = 0;
    int enroll = 0;
    String reqOp = "";
    String newUse = "";
    int count = 0;

    while(!userInput.equals(SENTINEL)){ // while userInput does not equal "quit" continue
        System.out.print("Code: ");
        code = input.next(); // accepting user input
        System.out.print("Cost of single copy: " );

        cost = input.nextDouble(); // here is where I am having issues

           /* I was thinking of putting in an if statment that would be
             if( user inputs a $) then{
              throw something
             }
                But Im not sure what exactly to put in the if statment
                or what i should throw */
        System.out.print("Current number of books: ");
        numBooks = input.nextInt();
        System.out.print("Prospective class enrollment: ");
        enroll = input.nextInt();
        System.out.print("Is this Required or Optional?(Enter R or O): ");
        reqOp = input.next();
        System.out.print("Is it New or Used?(Enter N or U): ");
        newUse = input.next();

Answer 1

您可以使用正则表达式来过滤next的值，然后再将其转换为double，而不是使用nextDouble。

cost = Double.parseDouble(input.next().replaceAll("[^\\d.]+", ""));

这将转换＆＃34; $ 13,465,398.09＆＃34;到＆＃34; 13465398.09＆＃34;。

Answer 2

你可以抓住InputMismatchException并使用消息终止程序，或者你可以给cost一些其他值：

try {
    userExtraPercent = input.nextDouble();   
} catch (InputMismatchException e){ 
    System.out.println("Bad input");
    return;
}

或者，就像你说的那样，你可以允许一个$，但是你必须进行一些其他解析（例如用next()读取并过滤掉坏字符），如{{ 1}}不起作用。

Answer 3

继承我的最终代码

      code = input.next(); // accepting user input
        System.out.print("Cost of single copy: " );
             cost1 = input.next().replaceAll("[^\\d.]+", ""); // Accounting for $
             double cost = Double.parseDouble(cost1); // converting cost to double

抛出异常？忽略双重内容

3 个答案: