Java 发票程序 - 将数量设置为 0 将价格设置为 0.0

Question

我几乎完成了这个程序，除了当我将价格或数量对象设置为负数时它不会设置为 0。说明说如果价格不是正数它应该设置为 0.0，如果数量不是正数，应设置为 0。这是我的代码，谁能告诉我哪里出错了。

这个练习是3.12 Invoice class form Deitel 10th edition How program:

public class Invoice {  
private String partNumber;
private String partDescription;
private int quantity;
private double priceperitem;
private double amount;  
public Invoice(String number, String partDescription, int quantity, double price)
{       
        this.partNumber = number;
        this.partDescription = partDescription;
        this.quantity = quantity;
        this.priceperitem = price;
}       
public void setPartNumber(String number)
{           
        partNumber = number;            
}       
public String getPartNumber()
{           
        return partNumber;
}   
public void setPartDescription (String description)
{           
        partDescription = description;
}       
    public String getPartDescription(){         
        return partDescription;         
    }   
    public void setQuantity(int count){         
        if(count > 0)
            quantity = 0;           
    }       
    public int getQuantity(){           
        return quantity;
    }   
    public void setPrice (double price){            
        if(price > 0.0)
            priceperitem = price;           
        if(price < 0.0)
            priceperitem = 0.0; 
    }       
    public double getPrice(){           
        return priceperitem;
    }   
    public double getInvoiceAmount(){           
         amount = getQuantity() * getPrice();           
         return amount;
    }       
}

import java.util.Scanner;
public class InvoiceTest {
public static void main(String[] args) {        
    int quantity;
    double price;
    double invoiceAmount;       
    Invoice invoice1 = new Invoice("1234","Hammer",-5, -39.75);     
    Scanner keyboard = new Scanner (System.in);     
    System.out.printf( "Part number: %s\n", invoice1.getPartNumber());
    System.out.printf( "Part Description: %s\n", invoice1.getPartDescription());
    System.out.printf( "Quantity: %s\n", invoice1.getQuantity());
    System.out.printf( "Price: %s\n", invoice1.getPrice());
 }
}

Answer 1

您正在检查条件 if price<0然后将价格设置为 0，在你的 setter 方法中，即在方法 setPrice 中.但是您正在为 price thorugh 构造函数传递 -ve 参数，它没有这样的检查。也添加 checkin 构造函数:-

public Invoice(String number, String partDescription, int quantity, double price)
{
    this.partNumber = number;
    this.partDescription = partDescription;
    this.quantity = quantity;

    if(price > 0.0)
     priceperitem = price;

    if(price < 0.0)
     priceperitem = 0.0; 

}

数量检查也是如此，在构造函数中以类似的方式添加数量检查。

另请注意，您在 setQuantity 中的条件无效，请将其更改为:-

  if(quantity > 0)
  this.quantity = price;

  if(quantity < 0)
  this.quantity = 0.0;