我正在尝试向 ArrayList 添加一个新对象。每个 Item 对象将具有 3 个属性：
- 项目编号
- 信息
- 成本
我还有 3 节课：
- 项目类定义存储在目录中的单个项目。
- Catalog 类维护 Item 对象的列表。
- 客户端类 w/main 方法。
我在 Item 类中有集合和获取，并且在 Catalog 中有 ArrayList。在客户端中，我可以选择添加、删除或编辑对象。如何正确地将新的 Item 对象添加到 ArrayList？
我让 Item 类编译得很好，但 Catalog 和 Client 类没有编译。这是我在 Catalog 类中遇到的错误：
Catalog.java:35: error: no suitable method found for add(int,String,double)listOfObjects.add(newItemId, newDescription, newCost);
method ArrayList.add(int,Item) is not applicable
(actual and formal argument lists differ in length)
method ArrayList.add(Item) is not applicable
(actual and formal argument lists differ in length)
下面是项目类的代码
Public class Item
{
private int itemNum;
private String info;
private double cost;
public Item()
{ //start constructor
itemNum = 0; //default values
info = "x";
cost = 0;
} //end constructor
public CatalogItem(int newItemNum, String newInfo, double newCost)
{ //start overload constructor
this.itemNum = newItemNum;
this.info = newInfo;
this.cost = newCost;
} //end overload constructor
以下是 itemNum 的设置/获取
public int getItemNum()
{ //start itemNum accessor
return itemNum;
} //end getItemNum
public void setItemNum(int newItemNum)
{ //start itemNum mutator
this.itemNum = newItemNum;
} //end setItemNum
} //end Item class
//下面是我的目录类
import java.util.*;
public class Catalog
{ //start class
private ArrayList<CatalogItem> listOfObjects = new ArrayList<CatalogItem>(100); //creates ArrayList
Item newItem = new Item(newItemNum, newInfo, newCost); //instantiates Item class
/*
public Catalog()
{ //start constructor
} //end constructor
*/
public void add(CatalogItem newItem) //method adds a new Item object to the array list
{ //start add
listOfObjects.add(newItem);
} //end add
public void add(int itemNum, String info, double cost) //accepts parameters from main method to add to new object
{ //start add
int newItemNum = itemNum;
String newInfo = info;
double newCost = cost;
newItem.setItemNum(newItemNum);
newItem.setInfo(newInfo);
newItem.setCost(newCost);
listOfObjects.add(newItemNum, newInfo, newCost);
} //end add
} //end class
下面是客户端类。它接收用户关于 itemNum、info 和 cost 的输入
import java.util.*; //allows use of Scanner class
public class Client
{ //start client class
public static void main(String[] args)
{ //start main
Catalog serv = new Catalog(); //creates instance of Catalog class
Scanner scan = new Scanner(System.in); //creates instance of Scanner class called scan
public void add(int itemNum, String info, double cost) //accepts parameters from main method to add to new object
{ //start add
int newItemNum = itemNum;
String newInfo = info;
double newCost = cost;
newItem.setItemNum(newItemNum);
newItem.setInfo(newInfo);
newItem.setCost(newCost);
listOfObjects.add(newItemNum, newInfo, newCost); //adds the object to the ArrayList
} //end add
}
任何帮助将不胜感激。