java - 调试变量时遇到问题可能未初始化错误

Question

我在文件中看到了很多类似的问题，但我找不到像我遇到的问题那样的场景。

下面是我的代码。我遇到了“finalPrice”和“grandTotalPrice”可能尚未初始化的错误。代码行接近程序的末尾。

应该通过上面的控制台输入为变量分配总数。我不确定错误是什么，或者为什么。任何人都可以请帮助我，并解释一下吗？

代码:

import java.util.*;


public class PictureFrames
{

    static Scanner console = new Scanner(System.in);

    static final double REGULAR_FRAME = .15, FANCY_FRAME = .25;
    static final double COLOR = .10, CARDBOARD = .02, GLASS = .07, CROWNS = .35;


    public static void main (String[] args)
    {

    double length, width, area, perimeter; 
    double priceOfFrame, priceOfColor, priceOfCardboard, priceOfGlass, priceOfCrowns, finalPrice, crownFinalPrice, grandTotalPrice; 
    int numberOfCrowns;
    char typeOfFrame, choiceOfColor, choiceOfCrowns;



    System.out.println ("Please enter the length of your picure in inches:");
    length = console.nextDouble();

    System.out.println ("Please enter the width of your picure in inches: ");
    width = console.nextDouble();

    System.out.println ("Please enter the type of frame: R or r (Regular), F or f (Fancy). ");  
    typeOfFrame = console.next().charAt(0);

    System.out.println ("Would you like to add color?: Y for (Yes), N for (No): "); 
    choiceOfColor = console.next().charAt(0);


    switch (typeOfFrame)
    {
    case 'R':
    case 'r':
        if (choiceOfColor == 'N')
        {
            area = (length * width);
            perimeter = (2 * length) + (2 * width);
            priceOfFrame = (perimeter * REGULAR_FRAME);
            priceOfCardboard = (area * CARDBOARD);
            priceOfGlass = (area * GLASS);
            finalPrice = (priceOfFrame + priceOfCardboard + priceOfGlass);
        break;
        }
        else if (choiceOfColor == 'Y')
        {
            area = (length * width);
            perimeter = (2 * length) + (2 * width);
            priceOfColor = (area * COLOR);          
            priceOfFrame = (perimeter * REGULAR_FRAME);
            priceOfCardboard = (area * CARDBOARD);
            priceOfGlass = (area * GLASS);      
            finalPrice = (priceOfFrame + priceOfColor + priceOfCardboard + priceOfGlass);       
        break;
        }
    case 'F':
    case 'f':
        if (choiceOfColor == 'N')
        {
            area = (length * width);
            perimeter = (2 * length) + (2 * width);
            priceOfFrame = (perimeter * FANCY_FRAME);
            priceOfCardboard = (area * CARDBOARD);
            priceOfGlass = (area * GLASS);
            finalPrice = (priceOfFrame + priceOfCardboard + priceOfGlass);
        break;
        }
        else if (choiceOfColor == 'Y')
        {
            area = (length * width);
            perimeter = (2 * length) + (2 * width);
            priceOfColor = (area * COLOR);          
            priceOfFrame = (perimeter * FANCY_FRAME);
            priceOfCardboard = (area * CARDBOARD);
            priceOfGlass = (area * GLASS);      
            finalPrice = (priceOfFrame + priceOfColor + priceOfCardboard + priceOfGlass);       
        break;
        }

}       

    System.out.println ("Would you like to add crowns? Enter Y (Yes), or N (No): ");    
    choiceOfCrowns = console.next().charAt(0);

    if (choiceOfCrowns == 'Y')
    {
        System.out.println ("How many crowns would you like? ");    
        numberOfCrowns = console.nextInt();     
        crownFinalPrice =(numberOfCrowns * CROWNS);
        grandTotalPrice = (crownFinalPrice + finalPrice);
    }   
    else if (choiceOfCrowns == 'N')
            System.out.printf ("Your total comes to: $%.2f%n", grandTotalPrice);    

    }   

}

Answer 1

如果 typeOfFrame 不是 R、r、F 或 f，会发生什么？
一种可能的解决方案是向开关添加“默认”情况。

我认为这段代码更接近你想要的(我减少了很多重复)。请注意，我并没有真正处理错误(对 isValidChoice 和 isFrameType 方法的调用是如何处理它们的开始)。上面的问题是，您基本上假设用户只会输入有效的输入，而忘记了有时即使 Y 和 N 是他们可以在 Q 中输入的唯一有效选项。我还修复了一个错误您并不总是打印出总计，也没有设置总计(printf 上方的最后一部分)。

我的最后一个建议是不要为此使用 double (除非你的教练告诉你)，因为在某些情况下他们会给你不准确的数字。看看 java.math.BigDecimal 吧。

class Main
{
    static Scanner console = new Scanner(System.in);    
    static final double REGULAR_FRAME = .15;
    static final double FANCY_FRAME = .25;
    static final double COLOR = .10;
    static final double CARDBOARD = .02;
    static final double GLASS = .07;
    static final double CROWNS = .35;

    public static void main (String[] args)
    {   
        final double length;
        final double width;
        final char   typeOfFrame;
        final char   choiceOfColor;

        System.out.println ("Please enter the length of your picure in inches:");
        length = console.nextDouble();

        System.out.println ("Please enter the width of your picure in inches: ");
        width = console.nextDouble();

        System.out.println ("Please enter the type of frame: R or r (Regular), F or f (Fancy). ");  
        typeOfFrame = console.next().charAt(0);

        System.out.println ("Would you like to add color?: Y for (Yes), N for (No): "); 
        choiceOfColor = console.next().charAt(0);

        if(!(isFrameType(typeOfFrame)))
        {

        }
        else
        {
            final double area;
            final double perimeter; 
            final double priceOfFrame;
            final double priceOfCardboard;
            final double priceOfGlass;

            area             = (length * width);
            perimeter        = (2 * length) + (2 * width);
            priceOfFrame     = (perimeter * REGULAR_FRAME);
            priceOfCardboard = (area * CARDBOARD);
            priceOfGlass     = (area * GLASS);  

            if(isValidChoice(choiceOfColor))
            {
                final double priceOfColor;
                final double finalPrice;
                final char   choiceOfCrowns;
                final double grandTotalPrice; 

                if(choiceOfColor == 'N')
                {
                    finalPrice = (priceOfFrame + priceOfCardboard + priceOfGlass);
                }
                else
                {
                    priceOfColor = (area * COLOR);          
                    finalPrice   = (priceOfFrame + priceOfColor + priceOfCardboard + priceOfGlass);     
                }    

                System.out.println ("Would you like to add crowns? Enter Y (Yes), or N (No): ");    
                choiceOfCrowns = console.next().charAt(0);

                if(isValidChoice(choiceOfCrowns))
                {
                    if(choiceOfCrowns == 'Y')
                    {
                        final double crownFinalPrice;
                        final int    numberOfCrowns;

                        System.out.println ("How many crowns would you like? ");    
                        numberOfCrowns  = console.nextInt();        
                        crownFinalPrice =(numberOfCrowns * CROWNS);
                        grandTotalPrice = (crownFinalPrice + finalPrice);
                    }   
                    else
                    {
                        grandTotalPrice = finalPrice;
                    }

                    System.out.printf ("Your total comes to: $%.2f%n", grandTotalPrice);    
                }
            }
        }
    }   

    private static boolean isFrameType(final char c)
    {        
        final char lower;

        lower = Character.toLowerCase(c);

        return (lower == 'r' || lower == 'f');
    }

    private static boolean isValidChoice(final char c)
    {
        return (c == 'Y' || c == 'N');
    }
}