如何正确地从ArrayList中删除对象？
如何正确地从ArrayList中删除对象？
提问于 2013-10-07 17:01:30
我正在尝试从ArrayList中删除对象。每个Item对象有3个属性: 1. itemNum；2.信息；3.成本。我还有3个类，1. Item类定义了存储在目录中的单个项目。2. Catalog类维护Item对象的列表。3使用main方法的客户机类。我在Item类中有sets和gets，在Catalog中有ArrayList。在客户端，我会提示“Enter In the itemNum to remove.如何根据对itemNum的搜索从ArrayList中正确删除Item对象？下面是我的代码和到目前为止我已经尝试过的代码。
Public class Item
{
private int itemNum;
private String info;
private double cost;
private int itemNum;
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//下面是itemNum的set/gets。我也有成本和信息的设置/获取，但选择不包括do to space
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
public boolean equals(CatalogItem obj)
{ //start equals
if (itemId == obj.itemId)
return true;
else
return false;
} //end equals//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);
public void remove(int id)
{ //start remove
int item = id;
for (int index = 0; index < listOfObjects.size(); index++)
if (newItem.getItemId() == item) //if item in the inventory matches the item number passed
listOfObjects.remove(index); //removes based on index, I’ve also tried listOfObjects.remove(item);
/* I’ve also tried an enhanced for loop
for (CatalogItem obj : listOfObjects)
if (newItem.getItemId() == item)
listOfObjects.remove(newItem); */
} //end remove}
//下面是main。它接收来自用户的关于itemNum、信息和成本的输入
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
System.out.print("\nEnter in the Item ID you want to remove: ");
id = scan.nextInt();
serv.remove(id); //sends id to Catalog Class to be removed
} //end main
} //end class它可以很好地编译，但不会根据找到的索引删除。任何帮助都是最好的。
Stack Overflow用户
发布于 2013-10-07 17:28:33
要从列表中删除对象，您需要首先找到该对象。您可以实现Comparable接口并重写compareTo()方法来查找对象。
Public class CatalogItem implements Comparable
{
private int itemNum;
private String info;
private double cost;
private int itemNum;
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
public int compareTo(catalogItem c){
if(c.getItemNum == this.getItemNum()){
return 0;// zero means both are equal
}
}
}当您获得itemNum表单输入时，创建一个CatalogItem对象并设置此值，然后遍历list以检查相等性。如果您找到它，则从列表中删除，但请确保您没有从相同的列表中删除，否则您可能会得到Concurrency Exception。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/19220691
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