如何复制数组列表以不反映原始列表中的更改？ [英] How to copy an arraylist to not reflecting changes in the original list?

问题描述

如何将列表复制到另一个列表，并对新列表中包含的对象进行更改，而不影响旧列表中的对象？

How can I copy a list to another list, and make changes to the objects contained in the new list, without affecting the objects in the old list?

class Foo {
   String title;
   void setTitle(String title) { this.title = title; }
}

List<Foo> original;
List<Foo> newlist = new ArrayList<Foo>(original);

for (Foo foo : newlist) {
   foo.setTitle("test"); //this will also affect the objects in original list.
                         //how can I avoid this?
}

推荐答案

对象，但是你必须实现一个克隆方法才能工作。换句话说，没有一个简单的，一般的交钥匙解决方案。

You will have to clone the objects, but then you have to implement a clone method for it to work. In other words, there is not a simple, general turnkey solution.

List<Foo> original;
List<Foo> newList=new ArrayList<Foo>();

for (Foo foo:original){
    newList.add(foo.clone();
}

//Make changes to newList

在列出的案例中，克隆可以是：

In the listed case clone could be:

class Foo {

    String title;

    void setTitle(String title) { this.title = title; }

    Foo clone(Foo foo){
        Foo result=new Foo();
        result.setTitle(foo.title);
        return result;
    }
}

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