Question

我需要让变量orderNum为每个订单号增加1.现在这是在一个switch语句中我尝试了一个for循环和orderNum ++但是happing是什么，orderNum只给我1个每个语句。所以我不确定我在哪里出错了我已经搜索了网但却找不到答案。

感谢您的帮助

public class orders extends javax.swing.JFrame{

private char productName;
private char productCode;
private double price;
private double discount;
private int quantity;
private double total;
private String message;
private int orderNum;
private final double MAXORDER = 1000;
private final double MINORDER = 0.1;

orders(char productCode, int quantity) {
 this.productCode = productCode;
 this.quantity = quantity;
 }
public String calculate() {
 double price = 0;
//int i = 0;
 String productName= " ";
 boolean isDiscounted = false;
 boolean isValidOrder = true;

 if (quantity > MAXORDER){
   message = "**ERROR** Invalid quantity. Quantity cannot be greater than 1000";
   isValidOrder = false;
    }
else if (quantity < MINORDER){
    message = "**ERROR** Invalid quantity. Quantity cannot be  0 or less ";
    isValidOrder = false;
}

 if (isValidOrder) {
 int orderNum =0;
 // while (i<100){ 
 switch (productCode) {
     case 'A':
         orderNum+=1;

         productName = "Pencil";
         price = quantity * 0.60;

         break;

     case 'b':
        orderNum+=1;

         productName = "Rubber";
         price = quantity * 0.90;

         break;

     case 'c':
         orderNum+=1;
         productName = "Meat";
         price = quantity * 100.00;

         break;

         default:
         isValidOrder = false;
         message = "Not this time";
         break;
        }

      if(isValidOrder){
     message = "Order Number: " + orderNum + "\n" + "You are buying " + productName +        "\n" + "The quantity of: " + quantity + "\n" + "For the price of $" + price;
     System.out.println("Tom is : " + orderNum);
     }
     }
// }
  return message;
  }   
 }

Answer 1

您刚刚将orderNum声明为0，我认为您希望将其作为班级成员。另外，我建议使用++而不是+= 1。像

这样的东西

private static int orderNum = 0;

public String calculate() {
    double price = 0;
    // int i = 0;
    String productName = " ";
    boolean isDiscounted = false;
    boolean isValidOrder = true;

    if (quantity > MAXORDER) {
        message = "**ERROR** Invalid quantity. Quantity cannot be greater than 1000";
        isValidOrder = false;
    } else if (quantity < MINORDER) {
        message = "**ERROR** Invalid quantity. Quantity cannot be  0 or less ";
        isValidOrder = false;
    }

    if (isValidOrder) {
        // while (i<100){
        switch (productCode) {
        case 'A':
            orderNum++;
            productName = "Pencil";
            price = quantity * 0.60;
            break;
        case 'b':
            orderNum++;
            productName = "Rubber";
            price = quantity * 0.90;
            break;
        case 'c':
            orderNum++;
            productName = "Meat";
            price = quantity * 100.00;
            break;
        default:
            isValidOrder = false;
            message = "Not this time";
            break;
        }

        if (isValidOrder) {
            message = "Order Number: " + orderNum + "\n"
                    + "You are buying " + productName + "\n"
                    + "The quantity of: " + quantity + "\n"
                    + "For the price of $" + price;
            System.out.println("Tom is : " + orderNum);
        }
    }
    // }
    return message;
}

Answer 2

您正在定义两个orderNum变量：类成员字段和方法内的局部变量。对于每个方法调用，局部变量将始终初始化为零，因此您需要将其删除以增加字段变量。

Answer 3

你有shadowed orderNum变量，在if(isValidOrder)之后声明它，删除它，一切都应该没问题

Java在switch语句中递增1

3 个答案: