如何从ArrayList中删除元素? [英] How to remove element from ArrayList?

问题描述

我已将数据添加到 ArrayList 中，现在想要更新该列表并从中删除一些元素.

I have added data into ArrayList and now want to update that list be deleting some element from it.

我在类型为 CartEntry 的 ArrayList 中有类似 1,2,3,4 的元素.

I have element something like 1,2,3,4 in ArrayList of type CartEntry.

代码:

ArrayList<CartEntry> items = new ArrayList<CartEntry>();

public void remove(int pId)
{
    System.out.println(items.size());

    for(CartEntry ce : items)
    {
        if(ce.getpId() == pId)
        {
            items.remove(ce);
            //System.out.println(items.get(1));             
        }
    }   
    items.add(new CartEntry(pId));
}

购物车入口代码:

public long getpId() {
    return pId;
}

构造函数:

public CartEntry(long pId) {
    super();
    this.pId = pId;     
}

当我尝试这段代码时，它给了我一个错误:

when I am trying this code it gives me an error:

java.util.ConcurrentModificationException
    at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
    at java.util.ArrayList$Itr.next(Unknown Source)

这里的 pId 是指定应从项目中删除项目的参数.假设我想删除有 2 个数据的项目，那么我必须做什么?

Here pId is the argument that specify that item should be deleted from items. Suppose I want to delete item that have 2 data then what will I have to do ?

推荐答案

您面临 ConcurrentModificationException 因为您同时对同一个 list 执行两个操作.即循环和删除同一时间.

You are facing ConcurrentModificationException because you are doing two operations on the same list at a time. i.e looping and removing same time.

为了避免这种情况，请使用迭代器，它可以保证您安全地从列表中删除元素.

Inorder to avoid this situation use Iterator,which guarantees you to remove the element from list safely .

一个简单的例子看起来像

A simple example looks like

Iterator<CartEntry> it = list.iterator();
    while (it.hasNext()) {
        if (it.next().getpId() == pId) {
            it.remove();
            break;
        }
    }

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