從類ojects創建數組或ArrayList

Question

我一直在這一段時間，但似乎無法弄清楚如何將項目添加到ArrayList。我想補充grocItem（應該是從for循環的用戶輸入7個grocItems）插入grocList的ArrayList：

 public class ItemData{ 
     public ItemData(String name, double cost, int priority){ 

     Main.(ArrayList grocList).add(grocItem); 

      // Main.groclist.add(grocItem); 



    } 
} 

主類：

import java.util.*; 


public class Main { 

    public static List<ItemData> itemData = new ArrayList<ItemData>(); 
    public static void main(String[] args) { 
     int i=0; 
     //String name1; 
     //int priority1; 
     //double cost1; 

     String[] item = new String[7]; 

     for (i=0; i<item.length; i++) { 
      Scanner keyboard = new Scanner(System.in); 
      System.out.println("Enter item name " + i); 
      String name = keyboard.next(); 
      Scanner keyboard2 = new Scanner(System.in); 
      System.out.println("Enter the price of item " + i); 
      double cost = keyboard2.nextDouble(); 
      Scanner keyboard3 = new Scanner(System.in); 
      System.out.println("Enter Priority Number " + i); 
      int priority = keyboard3.nextInt(); 

      ItemData grocItem = new ItemData(name, cost, priority); 
     } 
     //How do I add grocItem to an Array list of other grocItems (6 grocItems from user input array item) 
     Main.itemData.add(groclist); 

    } 
} 

Answer 1

更改代碼，添加內部的方法循環。

for (i=0; i<item.length; i++) { 
      Scanner keyboard = new Scanner(System.in); 
      System.out.println("Enter item name " + i); 
      String name = keyboard.next(); 
      Scanner keyboard2 = new Scanner(System.in); 
      System.out.println("Enter the price of item " + i); 
      double cost = keyboard2.nextDouble(); 
      Scanner keyboard3 = new Scanner(System.in); 
      System.out.println("Enter Priority Number " + i); 
      int priority = keyboard3.nextInt(); 

      ItemData grocItem = new ItemData(name, cost, priority); 
      itemData.add(grocItem); // add here 
     } 

Answer 2

您應該ItemData對象添加到您的ArrayList內循環：

for (i=0; i<item.length; i++) { 
     Scanner keyboard = new Scanner(System.in); 
     System.out.println("Enter item name " + i); 
     String name = keyboard.next(); 
     Scanner keyboard2 = new Scanner(System.in); 
     System.out.println("Enter the price of item " + i); 
     double cost = keyboard2.nextDouble(); 
     Scanner keyboard3 = new Scanner(System.in); 
     System.out.println("Enter Priority Number " + i); 
     int priority = keyboard3.nextInt(); 

     ItemData grocItem = new ItemData(name, cost, priority); 
     itemData.add(groclist); // <-- add to arraylist inside the loop 

}