java - 我的 java 类验证不起作用，为什么？

Question

如果数量不是正数，则应设置为 0。如果每件商品的价格不是正数，则应设置为 0.0。然而，当我输入负数时，它会继续将我的变量设置为负而不是零。

这是我的类包 com.company;

/**
 * Created by juliodiaz on 5/7/16.
 */
public class Invoice {

    private String partNumber;
    private String partDescription;
    private int partQuantity;
    private double partPrice;

    public Invoice(String partNumber, String partDescription, int partQuantity, double partPrice) {
        this.partNumber = partNumber;
        this.partDescription = partDescription;
        this.partQuantity = partQuantity;
        this.partPrice = partPrice;
    }

    public String getPartNumber() {
        return partNumber;
    }

    public void setPartNumber(String partNumber) {
        this.partNumber = partNumber;
    }

    public String getPartDescription() {
        return partDescription;
    }

    public void setPartDescription(String partDescription) {
        this.partDescription = partDescription;
    }

    public int getPartQuantity() {
        return partQuantity;
    }

    public void setPartQuantity(int partQuantity) {
        this.partQuantity = partQuantity;
    }

    public double getPartPrice() {
        return partPrice;
    }

    public void setPartPrice(double partPrice) {
        this.partPrice = partPrice;
    }

    public double invoiceAmountMethod(double partPrice, int partQuantity) {
        if (partQuantity < 0 || partPrice < 0.0) {
            this.partQuantity = 0;
            return partPrice * partQuantity;
        }
        else
            return partPrice * partQuantity;
    }
}

//Main method
package com.company;

public class Main {

    public static void main(String[] args) {
        // write your code here

        Invoice myTruck = new Invoice("A101", "Wheels", -2, 100.00);

        System.out.println(myTruck.getPartDescription());
        System.out.println(myTruck.getPartNumber());
        System.out.println(myTruck.getPartQuantity());
        System.out.println(myTruck.getPartPrice());

        double price = myTruck.getPartPrice();
        int quantity = myTruck.getPartQuantity();

        System.out.println("The total cost is " + myTruck.invoiceAmountMethod(price, quantity));

    }
}

输出

Wheels
A101
-2
100.0
The total cost is -200.0

Answer 1

您正在分配:

this.partQuantity = 0;

但你返回:

return partPrice * partQuantity;

(传递给方法的参数)。

您可以通过返回来修复它:

return this.partPrice * this.partQuantity;

并且您确实不应该向此方法传递任何参数。