Question

我在代码“ main”中的异常中不断收到此异常

java.util.IllegalFormatConversionException：f！= java.lang.Integer

我不知道如何解决格式转换。帮助将不胜感激。

import javax.swing.JOptionPane;
public class SoftwareSales {
public static void main(String[] args) {
// This program displays the amount of discount (if any) and the total amount of the purchase after the discount.

    String userInput;
    String userOutput;
    double packagePrice = 99;
    int userNumberOfPackages;
    double discount = 0;
    double subTotal = 0;
    double total = 0;

    userInput = JOptionPane.showInputDialog( "Enter how many packages you are buying" );
    userNumberOfPackages = Integer.parseInt( userInput );

    if ( userNumberOfPackages < 10){
        subTotal = packagePrice * userNumberOfPackages;
        discount = 0;
        total = subTotal - discount;

    } else if ( userNumberOfPackages < 20 ){
        subTotal = packagePrice * userNumberOfPackages;
        discount = ( (double)20/100) * subTotal;
        total = subTotal - discount;

    } else if ( userNumberOfPackages < 50 ){
        subTotal = packagePrice * userNumberOfPackages;
        discount = ( (double)30/100) * subTotal;
        total = subTotal - discount;

    } else if ( userNumberOfPackages < 100 ){
        subTotal = packagePrice * userNumberOfPackages;
        discount = ( (double)40/100) * subTotal;
        total = subTotal - discount;

    } else{
        subTotal = packagePrice * userNumberOfPackages;
        discount = ( (double)50/100) * subTotal;
        total = subTotal - discount;
    }

    userOutput = String.format( "Packages purchased: \nSubtotal: $\nDiscount: $\nTotal: $", userNumberOfPackages, subTotal,
            discount, total);

    JOptionPane.showMessageDialog( null, userOutput);

    System.exit(0);
}
}

Answer 1

让我们总结一下评论，因为它们不仅可以解决您的问题，而且可以描述任何问题的过程。

获取 all 异常信息。那就是类型，消息和调用栈。
查看调用堆栈，并确定自己编写的最高级的类。
获取行号。
看看那条线，思考潜在的问题。

适用于您的情况：

at java.util.Formatter$FormatSpecifier.failConversion(Formatter.java:4302) at
java.util.Formatter$FormatSpecifier.printFloat(Formatter.java:2806) at
java.util.Formatter$FormatSpecifier.print(Formatter.java:2753) at
java.util.Formatter.format(Formatter.java:2520) at
java.util.Formatter.format(Formatter.java:2455) at
java.lang.String.format(String.java:2940) at 
SoftwareSales.main(SoftwareSales.java:45)

只有SoftwareSales.java是您自己编写的。因此问题出在SoftwareSales.java，第45行。

是这一行：

userOutput = String.format( "Packages purchased: \nSubtotal: $\nDiscount: $\nTotal: $", userNumberOfPackages, subTotal,
            discount, total);

使用String.format()，您想在字符串中插入4个数字。但是应该将它们插入哪里？没有Placehoder。

看一些documentation：

format：格式字符串

a format string需要带有%的内容。 %f可能是浮点数，%d可能是十进制数。

最后（未试用）：

userOutput = String.format( "Packages purchased: %d\n
       Subtotal: $%f\n
       Discount: $%f\n
       Total: $%f", 
       userNumberOfPackages, subTotal, discount, total);

线程“主”中的异常java.util.IllegalFormatConversionException：f！= java.lang.Integer

1 个答案: