Question

我的java程序无法正确计算折扣，我无法弄清楚原因。我是java的新手，我不知道如何解决这个问题，所以任何帮助都会受到赞赏。例如，如果你购买100个袋子，你的折扣应该是82.50，但是我说它是27.50

import java.text.DecimalFormat;
import java.util.Scanner;
public class Coffee {
    public static void main(String args[]){
        Scanner bags = new Scanner(System.in);
        System.out.println("Hello and welcome to the program");
        System.out.println("Here is the discount list for the IT125 Coffee Company");
        System.out.println("<= 24 Bags      No discount");
        System.out.println(">= 25 Bags      5% ");
        System.out.println(">= 50 Bags      10% ");
        System.out.println(">= 100 Bags     15% ");
        System.out.println(">= 150 Bags     20% ");
        System.out.println(">= 200 Bags     25% ");
        System.out.println(">= 300 Bags     30% ");
        System.out.println("");

        DecimalFormat df = new DecimalFormat("0.00");
        int num1;
        System.out.print("Enter the number of bags purchased: ");
        num1 = bags.nextInt();
        System.out.println("Bags purchased " + num1);
        double cost, disc, totcost;
        totcost = 0;
        disc = 0;
        cost = num1 * 5.50;
        System.out.println("Normal Price: € " + df.format(cost));



        if (num1 < 25) {
            System.out.println("Your dicount is " + disc);
            totcost = cost - disc;
            System.out.print("Your total cost is € " + df.format(totcost));
        }

        else if (num1 >= 25) {
            disc = cost * 0.05;
            totcost = cost - disc;
            System.out.println("Your dicount is € " + df.format(disc));
            System.out.print("Your total cost is € " + df.format(totcost));
        }

        else if (num1 >= 50) {
            disc = cost * 0.1;
            totcost = cost - disc;
            System.out.println("Your dicount is € " + df.format(disc));
            System.out.print("Your total cost is € " + df.format(totcost));
        }

        else if (num1 >= 100) {
            disc = cost * 0.15;
            totcost = cost - disc;
            System.out.println("Your dicount is € " + df.format(disc));
            System.out.print("Your total cost is € " + df.format(totcost));
        }

        else if (num1 >= 150) {
            disc = cost * 0.2;
            totcost = cost - disc;
            System.out.println("Your dicount is € " + df.format(disc));
            System.out.print("Your total cost is € " + df.format(totcost));
        }

        else if (num1 >= 200) {
            disc = cost * 0.25;
            totcost = cost - disc;
            System.out.println("Your dicount is € " + df.format(disc));
            System.out.print("Your total cost is € " + df.format(totcost));

        }

        else if (num1 >= 300) {
            disc = cost * 0.3;
            totcost = cost - disc;
            System.out.println("Your dicount is € " + df.format(disc));
            System.out.print("Your total cost is € " + df.format(totcost));
        }

    }

}

Answer 1

万恶之源：

 else if (num1 >= 25) {

这会捕获从25到无穷大的所有数字。使用

 else if(num1 < 50) {

等等。将所有数量分开到300以下后，最后一个分支将不需要测试。

我想补充说代码重复并不好。避免这种情况的一种方法是使用

int[] limit = new int[]{ 25, 50, 100, 150, 200, 300 };
int[] disct = new int[]{  5, 10,  15,  20, 25,   30 }

int d = 0;
for( int i = 0; i < limit.length; ++i ){ 
    if( qtty < limit[i] ) break;
    d = disct[i];
}

double cost = qtty*price;
double discount = cost*d/100;
totcost = cost - discount;

Answer 2

你已经将if块放在一个顺序中，使得大于25的任何东西都会被第二个阻塞，即使它足够大，可以被其中一个阻挡。 Java没有检查else if的列表;它几乎是逐行的，所以如果它看到350作为输入，它会看到它大于25并进入if块，即使它可以进入后来的一个。如果您颠倒订单，则会有if块，以便首先检查最大数字，它将正常工作。

Answer 3

我可以看到你的问题。

它位于您的if / else声明中。

想象一下，你将num1设为60。您显然希望在下面执行代码C，但不幸的是，它会执行代码B，因为它是导致if的第一个true：

下面：

   if (num1 < 25) {
     //A
   }
   else if (num1 >= 25) {
     //B
   }
   else if (num1 >= 50) {
     //C
   }

正确的if块将是：

   if (num1 < 25) {
     //A
   }
   else if (num1 >= 25 && num<50) {
     //B
   }
   else if (num1 >= 50) {
     //C
   }

这个例子并没有像你那样有很多条件，你需要在所有if语句中设置下限和上限，除了最后一个。

Answer 4

请尝试使用以下代码：添加边界条件。

import java.text.DecimalFormat;
import java.util.Scanner;
public class Coffee {
    public static void main(String args[]){
        Scanner bags = new Scanner(System.in);
        System.out.println("Hello and welcome to the program");
        System.out.println("Here is the discount list for the IT125 Coffee Company");
        System.out.println("<= 24 Bags      No discount");
        System.out.println(">= 25 Bags      5% ");
        System.out.println(">= 50 Bags      10% ");
        System.out.println(">= 100 Bags     15% ");
        System.out.println(">= 150 Bags     20% ");
        System.out.println(">= 200 Bags     25% ");
        System.out.println(">= 300 Bags     30% ");
        System.out.println("");

        DecimalFormat df = new DecimalFormat("0.00");
        int num1;
        System.out.print("Enter the number of bags purchased: ");
        num1 = bags.nextInt();
        System.out.println("Bags purchased " + num1);
        double cost, disc, totcost;
        totcost = 0;
        disc = 0;
        cost = num1 * 5.50;
        System.out.println("Normal Price: € " + df.format(cost));



        if (num1 < 25) {
            System.out.println("Your dicount is " + disc);
            totcost = cost - disc;
            System.out.print("Your total cost is € " + df.format(totcost));
        }

        else if (num1 >= 25 && num1<50) {
            disc = cost * 0.05;
            totcost = cost - disc;
            System.out.println("Your dicount is € " + df.format(disc));
            System.out.print("Your total cost is € " + df.format(totcost));
        }

        else if (num1 >= 50 && num1<100) {
            disc = cost * 0.1;
            totcost = cost - disc;
            System.out.println("Your dicount is € " + df.format(disc));
            System.out.print("Your total cost is € " + df.format(totcost));
        }

        else if (num1 >= 100 && num1<150) {
            disc = cost * 0.15;
            totcost = cost - disc;
            System.out.println("Your dicount is € " + df.format(disc));
            System.out.print("Your total cost is € " + df.format(totcost));
        }

        else if (num1 >= 150 && num1<200) {
            disc = cost * 0.2;
            totcost = cost - disc;
            System.out.println("Your dicount is € " + df.format(disc));
            System.out.print("Your total cost is € " + df.format(totcost));
        }

        else if (num1 >= 200 && num1<300) {
            disc = cost * 0.25;
            totcost = cost - disc;
            System.out.println("Your dicount is € " + df.format(disc));
            System.out.print("Your total cost is € " + df.format(totcost));

        }

        else if (num1 >= 300) {
            disc = cost * 0.3;
            totcost = cost - disc;
            System.out.println("Your dicount is € " + df.format(disc));
            System.out.print("Your total cost is € " + df.format(totcost));
        }

    }

}

输出：

Hello and welcome to the program
Here is the discount list for the IT125 Coffee Company
<= 24 Bags      No discount
>= 25 Bags      5% 
>= 50 Bags      10% 
>= 100 Bags     15% 
>= 150 Bags     20% 
>= 200 Bags     25% 
>= 300 Bags     30% 

Enter the number of bags purchased: 100
Bags purchased 100
Normal Price: € 550.00
Your dicount is € 82.50
Your total cost is € 467.50

Java程序无法正常工作

4 个答案: