初學者做Java項目

Question

• 第二個構造函數是接收兩個參數，productName和 數量。 productName參數將被分配給類的實例變量productName 。數量參數將傳遞給 testQuantity方法。在此之後，調用getPrice方法應使 傳遞給productName參數。僅當訂單有效時才需要調用計算方法

• 第三個構造函數是接收三個參數productName，數量爲 和折扣。
  productName參數將被分配給類的 productName實例變量。 testQuantity，getPrice和testDiscount方法都需要傳遞所需的參數。 僅當訂單有效時才需要調用計算方法。

這個問題得到了回答，並以此代碼結束。感謝您的幫助

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

我也仍然非常學習者，因此認識到，這是不容易提問的時候，你甚至不完全知道你是問什麼。

基於您的具有挑戰性的描述，我試圖編寫一個可以構建的示例程序。請閱讀我的評論，因爲我試圖描述性很強，以幫助你理解/學習。

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 
} 

我已經在類的底部添加了一些額外的領域，使我的例子更容易顯示出來，因爲我是爲你想怎麼你的一些方法，以工作非常不確定。我已經在您的構造函數中放置並初始化了這些元素，並對其進行了評論。

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 
} 

上述方法顯示由構造函數創建的順序的所有細節，並顯示它的細節以查看。

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; 
} 

我不確定你想用這種方法做什麼，所以都留下了空白。如果您需要存儲可用項目的總數來檢查數量，最好的辦法是數據庫，這需要一整套不同的學習。

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

如果用戶除總訂單價格外還有折扣，則返回折扣價格。兩者都是由您與構造

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; 
} 

上述開關也可能會被檢查項目的價格最好的方式來創建Order對象舉行。每個案例都有一個項目的名稱和價格。您使用該價格乘以數量創建訂單價格。

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); 
} 

從'main'方法創建兩個命令來測試我們的應用程序。

有一個修補程序和玩它。我不確定這是否是您希望從您的問題中得到的結果，但希望您能找到有用的方法。