Question

我是java的新手，不理解为什么它不起作用，并在2条“ ifs”行上说“ num无法解析为veriable”。谢谢您的帮助

package basicJava1;
import java.util.Scanner;
public class DiscountCalculator{
  static Scanner reader = new Scanner(System.in);
  public static void main(String[] args)
  {
    double ₪ = 3.5748;
    System.out.println("Enter the price");
    double price = reader.nextInt();
    //
    System.out.println("Enter the discount");
    double dis = reader.nextInt();
    //
    if (dis > 99) {
        System.out.println("error");
    }   else {  
        System.out.println("the price is" + " " + (price-dis*(price/100)));
        double priceafter = (price-dis*(price/100));
        System.out.println("Would you like to exchange the discounted price from $ to ₪? (1=yes/2=no)");
        int num= reader.nextInt();
    } 
    if(num = 1) {
        System.out.println("The price is " + ((price-dis*(price/100))*₪) + "₪");
    }   else    {
        if(num = 2) {
        System.out.println("The price is " + (price-dis*(price/100)) + "$");
        } else {
            System.out.println("error");
        }
    }
  }
}

Answer 1

num不在您使用的范围内，if(num = 1)也不是您想要的，因为单个=将1分配给num而不是比较它们。为了进行比较，请使用==。

将您的代码更改为以下内容：

...

int num = 0; // some reasonable sentinel value
if (dis > 99) {
    System.out.println("error");
    // more error handling probably needed
} else {  
    System.out.println("the price is" + " " + (price-dis*(price/100)));
    double priceafter = (price-dis*(price/100));
        System.out.println("Would you like to exchange the discounted price from $ to ₪? (1=yes/2=no)");
    num = reader.nextInt();
} 

if(num == 1) {
    System.out.println("The price is " + ((price-dis*(price/100))*₪) + "₪");
} else {
...

Answer 2

变量num在代码的第二部分中不可见，您需要在if...else语句之外声明该变量：

 public static void main(String[] args){
        int num = 0;
        double ₪ = 3.5748;
        System.out.println("Enter the price");
        ...
}

Answer 3

当前的实现中有很多错误：

=和if(num = 1)中的if(num = 2)应该改为==。 =用于分配值，==用于检查是否相等。
int num = reader.nextInt();在else块中，因此下一个if(num == 1)将不知道num变量。当前是您遇到的错误。

因此，请尝试以下操作：

import java.util.Scanner;
class Main{
  static Scanner reader = new Scanner(System.in);

  public static void main(String[] args){
    double ₪ = 3.5748;
    System.out.println("Enter the price");
    double price = reader.nextInt();
    //
    System.out.println("Enter the discount");
    double dis = reader.nextInt();
    //
    int num = 0;    // <- Now `num` is accessible by your second if-check below
    if(dis > 99){
      System.out.println("error");
    }else{
      double priceafter = price-dis*(price/100);
      System.out.println("the price is" + " " + priceafter);
      System.out.println("Would you like to exchange the discounted price from $ to ₪? (1=yes/2=no)");
      num = reader.nextInt();  // <- And we still set it here
    }

    if(num == 1){
      System.out.println("The price is " + ((price-dis*(price/100))*₪) + "₪");
    }else if(num == 2) {
      System.out.println("The price is " + (price-dis*(price/100)) + "$");
    }else{
      System.out.println("error");
    }
  }
}

Try it online.

需要注意的其他事项：

1：

System.out.println("the price is" + " " + (price-dis*(price/100)));
double priceafter = (price-dis*(price/100));

这里您要进行两次相同的计算，因此最好将其更改为：

double priceafter = price-dis*(price/100);
System.out.println("the price is" + " " + priceafter);

2：

if(num == 1){
  System.out.println("The price is " + ((price-dis*(price/100))*₪) + "₪");
}else{
  if(num == 2){
    System.out.println("The price is " + (price-dis*(price/100)) + "$");
  }else{
    System.out.println("error");
  }
}

我认为您实际上是在寻找if elseif else的情况，所以应该是这样：

if(num == 1){
  System.out.println("The price is " + ((price-dis*(price/100))*₪) + "₪");
}else if(num == 2){
  System.out.println("The price is " + (price-dis*(price/100)) + "$");
}else{
  System.out.println("error");
}

3。

double price = reader.nextInt();

这不是.nextDouble()吗？当您仅接受整数输入时，为什么要以double开头。.discount输入也是如此。

但是我今天确实因为你而学到了一些新东西。从来不知道₪是有效的变量名。我猜它起某种特殊的字母的作用，因为通常只有字母_或$是有效的变量名（和数字）也可以使用，但不能用作单个变量数字或在变量开头。）

num无法解析为真值

3 个答案: