Question

总而言之，此代码应该询问客户姓名，会员级别和原始购买价格。它应该将所有这些存储在它们各自的变量中，如果输入了除接受的成员级别之外的其他内容，则程序应该退出。存储完所有变量后，客户的名称，会员级别，原始购买价格，促销价格和保存金额应以本文末尾的格式打印出来。在此先感谢您的帮助！

import java.util.*;
public class Discount{
  public static void main(String[] args){
    Scanner keyboard = new Scanner(System.in);
    double purchase = 0.0;
    double platinum = (purchase * .2);
    double gold = (purchase * .15);
    double silver = (purchase * .1);
    String Platinum = null;
    String Gold = null;
    String Silver = null;
    String customerName = null;
    String level = null;
    double discount = 0.0;

    System.out.print("Please enter a customer name: ");
    customerName = keyboard.nextLine();
    System.out.print("Please enter the customer's member level: ");
    level = keyboard.nextLine();

    if (!level.equals("Platinum") && !level.equals("Gold") && !level.equals("Silver"))
    {
        System.exit(0);
    }

    System.out.print("Please enter the origianl purchase price: ");
    purchase = keyboard.nextDouble();

    System.out.println("Congratualations, " + customerName + "!");

    if (level.equals("Platinum") && purchase > 500)
    {
        discount = (platinum + (purchase*.05));
        System.out.println("As a " + level + " level cardholder, you have received a 25% discount during Bedlam.");
    }
    else if (level.equals("Platinum"))
    {
        discount = (platinum);
        System.out.println("As a " + level + " level cardholder, you have received a 20% discount during Bedlam.");
    }
    else if (level.equals("Gold"))
    {
        discount = (gold);
        System.out.println("As a " + level + " level cardholder, you have received a 15% discount during Bedlam.");
    }
    else if (level.equals("Silver"))
    {
        discount = (silver);
        System.out.println("As a " + level + " level cardholder, you have received a 10% discount during Bedlam.");
    }

一切正常，直到这一点，如果我将M作为customerName，Silver作为级别，500.20作为购买，这是在命令提示符中输出的内容： Congratualations, M! As a Silver level cardholder, you have received a 10% discount during Bedlam. Exception in thread "main" java.util.IllegalFormatConversionException: f != java.lang.String at java.util.Formatter$FormatSpecifier.failConversion(Unknown Source) at java.util.Formatter$FormatSpecifier.printFloat(Unknown Source) at java.util.Formatter$FormatSpecifier.print(Unknown Source) at java.util.Formatter.format(Unknown Source) at java.io.PrintStream.format(Unknown Source) at java.io.PrintStream.printf(Unknown Source) at Discount.main(Discount.java:62)

    System.out.printf("%.2f\n", "Original purchase price: $" + purchase);
    System.out.printf("%.2f\n", "Promotional price: $" + discount);
    System.out.printf("%.2f\n", "Amount saved: $" + (purchase-discount));

如果成功执行，它应该是这样的：

Congratulations, Marge Simpson!
As a Silver level cardholder, you received a 10% discount during Bedlam.
Original purchase price: $500.20
Promotional price: $450.18
Amount saved: $50.02 */
    }
}

Answer 1

请参阅this。试试这个语法：

System.out.println( "Original purchase price: $" + String.format("%.2f",purchase));
System.out.println("Promotional price: $" + String.format("%.2f",discount));
System.out.println("Amount saved: $" + String.format("%.2f", purchase-discount));

Answer 2

现在你基本上将整个字符串"Original purchase price: $" + purchase作为%.2f的参数传递。请改用String.format：

System.out.println("Original purchase price: $" + String.format("%.2f", purchase));

这也消除了将"\n"附加到字符串的需要，因为您可以使用System.out.println。

对某些代码进行调试很困难，这些代码可以计算出各种会员级别所能获得的折扣

2 个答案: