复制java hashmap [英] copying a java hashmap

问题描述

我试图保留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

我做

myojbectsListA = new myojbectsList();
myojbectsListB = new myobjectsList();

然后：将一些hashmap项目添加到A（like2）

then: Add some hashmap items to A (like2)

然后

myobjectListB = myobjectListA; //B has 2

然后：将hashmap项目添加到A; （如4个）

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

然后将A返回到存储在B中的项目;

then return A to the items stored in B;

myobjectListA = myobjectListb;

但是当我这样做时，B随A增长，而我正在向A添加hashmap项。
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.

我想A在最后一次测试后仍有原来的2结束
在C ++中我会使用复制与对象，什么是对等的？

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

添加：OK我留了一些东西解释this.MyObjectsList不包含HashMap，它是从类MyBaseOjbectsList派生有HashMap成员和MyObjectsList扩展MyBaseOjbectsList。这是不一样的。

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，你需要构建一个新的。 / p>

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

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

这将创建一个（浅）地图副本。

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

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