當我將它傳遞給一個方法時，如何讓我的用戶輸入訪問我的ArrayList

Question

以下是我目前使用的代碼。這是錯誤，我得到了58行

incompatible types required: ArrayList found:
VendProduct

（Alt-Enter組合顯示提示）

//自動售貨機分發多個產品

package newvendingmachine; 

import java.util.ArrayList; 
import java.util.Scanner; 

//Tony Moore 

public class NewVendingMachine{ 
    //Set class data 
    static String[] product = {"Chips", "M&Ms", "Peanuts", "Popcorn", "Snickers"}; 
    static Float[] cost = {.50f, .75f, .75f, .75f, .90f}; 
    static Integer[] inventory = {20, 20, 20, 20, 20}; 

    /** 
    * @param args the command line arguments 
    */ 
    public static void main(String[] args) { 
     ArrayList<VendProduct> vp = new ArrayList<>(); 
     for (int idx=0; idx<product.length; idx++) { 
      vp.add(new VendProduct()); 
     } 

     //Accept user input 
     Scanner input = new Scanner(System.in); 
     int userInput; 

     while (true) { 
      // Display menu graphics 

      System.out.println(" Options: Press your selection then press enter "); 
      System.out.println(" 1. "+product[0]+" "); 
      System.out.println(" 2. "+product[1]+" "); 
      System.out.println(" 3. "+product[2]+" "); 
      System.out.println(" 4. "+product[3]+" "); 
      System.out.println(" 5. "+product[4]+" "); 
      System.out.println(" 6. Quit "); 


      userInput = input.nextInt(); 

      if (userInput <1 || userInput >6) { 
       System.out.println("Please make a vaild selection");  
      } 

      if (userInput >=1 || userInput <=6) { 
       vp = (VendProduct)vp.get(userInput-1); 
       vp.buyProduct();   
      } 

      if (userInput == 6) { 
       System.out.println("Thanks, and come back soon"); 
       break; 
      } 
     } 
    } 
} 

Answer 1

vp = (VendProduct)vp.get(userInput-1);

vp是一個VendProduct的ArrayList，但您試圖將其設置爲僅一個VendProduct ...

您應該創建類型VendProduct的變量和使用，就像這樣：

VendProduct product = vp.get(userInput-1); 
product.buyProduct(); 

你也可以做vp.get(userInput-1).buyProduct();直接一行。這取決於你。使用兩行代碼通常會使代碼更清晰，更易於閱讀。