是否可以在Java中复制对象而不修改类本身（例如添加复制构造函数）？

Question

In my project I use an object from an external library, I need to make a copy of this object but I cannot modify the class in the library. How can I do that?

This is the class of the object that I must copy:

public class Tree<T> implements Iterable<Tree<T>> {
    private List<Tree<T>> children;
    private T value;
    private Tree<T> tree = this;

     ... 
    }

Answer 1

您可以扩展该类，根据需要实现特定的对象，并可以在其中添加其他功能。

Answer 2

If the class doesn't implement Cloneable, there isn't a good way of doing this.

The acceptable way of doing it is just to write a utility method to copy the class manually, but that assumes you have some understanding of its internal structure.

For example, you can do a shallow copy as follows:

T newTree = new T();
for (T t : tree) {
    newTree.add(t);
}

But since your class contains sub-trees, those won't be copied; it would only be a shallow copy (the new tree would contain references to the subtrees in the old tree).

For a deep copy, you will have to recursively copy the subtrees as well. I don't really understand enough about the structure of your class to write code for it.