初学者做Java项目

Question

• 第二个构造函数是接收两个参数，productName和 数量。 productName参数将被分配给类的实例变量productName 。数量参数将传递给 testQuantity方法。在此之后，调用getPrice方法应使 传递给productName参数。仅当订单有效时才需要调用计算方法

• 第三个构造函数是接收三个参数productName，数量为 和折扣。
  productName参数将被分配给类的 productName实例变量。 testQuantity，getPrice和testDiscount方法都需要传递所需的参数。 仅当订单有效时才需要调用计算方法。

这个问题得到了回答，并以此代码结束。感谢您的帮助

public Order() { 
     isValidOrder = false; 
     message = "**ERROR** Order number cannot be totalled as no details have been supplied."; 
     orderNum++; 
    } 

    public Order(String productName, int quantity){ 
     this.productName = productName; 
     this.quantity = quantity; 
     getPrice(this.productName); 


     if(isValidOrder != false){ 
      calculate(); 
     } 
     orderNum++; 

    } 

public Order(String productName, int quantity, int discount){ 
    this.productName = productName; 
    testQuantity(quantity); 
    getPrice(productName); 

     if(isValidOrder != false){ 
      calculate(); 
     } 
       orderNum++; 
} 

private String getOrderDetails(){ 
    message = message; 
    if(isValidOrder == true && isDiscounted == false){ 

     message = "Order Number: " + quantity + "\n" + "Product Name; " + productName + "\n" + "Product Price: $" + price + "\n" + "Order Quantity: " + quantity + "\n" + "Total Price: $" + total; 

    } else if(isValidOrder == true && isDiscounted == true){ 

     message = "Order Number: " + quantity + "\n" + "Product Name; " + productName + "\n" + "Product Price: $" + price + "\n" + "Order Quantity: " + quantity + "\n" + "Total Price: $" + total; 
    } else { 
     return message; 
    } 
    return message; 
} 

Answer 1

我也仍然非常学习者，因此认识到，这是不容易提问的时候，你甚至不完全知道你是问什么。

基于您的具有挑战性的描述，我试图编写一个可以构建的示例程序。请阅读我的评论，因为我试图描述性很强，以帮助你理解/学习。

public class Order { 

//Constructor 2 
public Order(String productName, int quantity) { 
this.productName = productName;//Get the name 
this.quantity = testQuantity(quantity); //Get the total quantity 
this.orderPrice =getPrice(productName, quantity); //Get the price of the order 
this.discountPrice = 0; //Should be set to a value, even though it won't be used in this constructor 
orderNum++; //Another order in, up the count :) 
displayOrder(productName, quantity, this.orderPrice, this.discountPrice); //Show order details 
} 

//Constructor 3 
public Order(String productName, int quantity, int discount) { 
this.productName = productName; //Get the name 
this.quantity = testQuantity(quantity); //Get the total quantity 
this.orderPrice = getPrice(productName, quantity); //Get the price of the order 
this.discountPrice = testDiscount(discount, this.orderPrice); //Get the price if there is a discount 

orderNum++; //Another order in, up the count :) 
displayOrder(productName, quantity, this.orderPrice, this.discountPrice); //Show order details 
} 

我已经在类的底部添加了一些额外的领域，使我的例子更容易显示出来，因为我是为你想怎么你的一些方法，以工作非常不确定。我已经在您的构造函数中放置并初始化了这些元素，并对其进行了评论。

private void displayOrder(String productName, int quantity, int orderPrice, int discountPrice){ 
if(discountPrice == 0){ //If the discount is 0 then there is no discount so the discount price is the same as the order price 
    discountPrice = orderPrice; 
} 
// \n is called an escape character and when in a string creates a new line. 
System.out.println("You have ordered: " + quantity + " " + productName + ("(s)") //Number and name of item ordered 
     + "\nTotal cost: £" + orderPrice + "\nPrice with Discount (If applicable)= £" + discountPrice //Order price and discount price displayed 
     + "\nOrder number: " + orderNum +"\n"); //Order Number 
} 

上述方法显示由构造函数创建的顺序的所有细节，并显示它的细节以查看。

private int testQuantity(int q){ 
//What you want to do in this method, 
//For example 
//System.out.println("You have ordered " + q + "Items"); 
return q; 
} 

我不确定你想用这种方法做什么，所以都留下了空白。如果您需要存储可用项目的总数来检查数量，最好的办法是数据库，这需要一整套不同的学习。

private int testDiscount(int discount, int orderPrice){ //Will return a discounted price and store it in 'discountPrice' field 
int reducedPrice = (orderPrice - discount); 
return reducedPrice; 
} 

如果用户除总订单价格外还有折扣，则返回折扣价格。两者都是由您与构造

private int getPrice(String productname, int quantity){ 
int price = 0; 
switch(productName){  //Switch so you can find what item ordered and allocate the correct price 
//Add cases for different items? 
case "Sweater": 
price = 10; 
break; 
default: 
price = 0; 
break; 
} 
    int totalPrice = price * quantity; //Work out price by multiplying quantity of item by price determined by switch 
return totalPrice; 
} 

上述开关也可能会被检查项目的价格最好的方式来创建Order对象举行。每个案例都有一个项目的名称和价格。您使用该价格乘以数量创建订单价格。

private String productName; //Name of product 
private int quantity;  //Quantity ordered 
private int orderPrice;  // The total order of the price 
private int discountPrice; //Somewhere to store the price of an order with a discount 
private static int orderNum; //This is static so that you it can be referenced even if no orders  have been made 


public static void main(String[] args){ //Test the ordering 
Order order1 = new Order("Sweater", 2); 
Order order2 = new Order("Sweater", 2, 5); 
} 

从'main'方法创建两个命令来测试我们的应用程序。

有一个修补程序和玩它。我不确定这是否是您希望从您的问题中得到的结果，但希望您能找到有用的方法。