在 Java 中复制 HashMap [英] Copying a HashMap in Java

问题描述

我正在尝试保留一个包含成员的类的临时容器:

I am trying to keep a temporary container of a class that contains member :

HashMap<Integer,myObject> myobjectHashMap

一个名为 myobjectsList 的类

A class called myobjectsList

那我做

myobjectsListA = new myobjectsList();
myobjectsListB = new myobjectsList();

然后:将一些 hashmap 项添加到 A(如 2)

then: Add some hashmap items to A (like 2)

然后:

myobjectListB = myobjectListA; //B has 2

然后:将 hashmap 项添加到 A(比如另外 4 个)

then: Add hashmap items to A (like 4 more)

然后:将A返回到B中存储的项目

then: return A to the items stored in B

myobjectListA = myobjectListb;

但是当我这样做时，当我向 A 添加哈希图项时，B 会随着 A 增长.A 现在有 6 个项目，因为 B 有 6 个.

But when I do this, B grows with A while I am adding hashmap items to A. A now has 6 items in it because B had 6.

我希望 A 在最后一次分配后仍然保留原来的 2.在 C++ 中我会使用对象的复制，java 的等价物是什么?

I want A to still have the original 2 at the end after last assignment. In C++ I would use copy with objects, what is the java equivalent?

补充:好的，我遗漏了一些东西来解释这一点.MyObjectsList 不包含 HashMap，它派生自具有 HashMap 成员的类 MyBaseOjbectsList 并且 MyObjectsList 扩展了 MyBaseOjbectsList.这有什么不同吗?

Added: OK I left something out explaining this. MyObjectsList does not contain the HashMap, it is derived from a class MyBaseOjbectsList which has the HashMap member and MyObjectsList extends MyBaseOjbectsList. Does this make a difference?

推荐答案

如果你想要一个 HashMap 的副本，你需要构造一个新的.

If you want a copy of the HashMap you need to construct a new one with.

myobjectListB = new HashMap<Integer,myObject>(myobjectListA);

这将创建地图的(浅)副本.

This will create a (shallow) copy of the map.

这篇关于在 Java 中复制 HashMap的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！