Java中的泛型类型的深度拷贝 [英] Deep Copy of a Generic Type in Java

问题描述

泛型类型的深拷贝（克隆）如何在Java中工作？是否有可能？

How does deep copies (clones) of generic types T, E work in Java? Is it possible?

E oldItem;
E newItem = olditem.clone(); // does not work

推荐答案

答案是否定的。因为没有办法在编译期间找出哪个类将替换泛型类型 E ，除非你将它绑定到一个类型。

The answer is no. Cause there is no way to find out which class will replace your generic type E during compile time, unless you Bind it to a type.

Java的克隆方式很浅，对于深层克隆，我们需要提供我们自己的实现。

Java way of cloning is shallow, for deep cloning, we need to provide our own implementation

解决它的办法是创建一个像这样的合同。

The work-around for it, is to create a contract like this

public interface DeepCloneable {
    Object deepClone();
}

并且实现者应该拥有自己的深度克隆 logic

and an implementor should be having its own deep-clone logic

class YourDeepCloneClass implements DeepCloneable {

    @Override
    public Object deepClone() {
        // logic to do deep-clone
        return new YourDeepCloneClass();
    }

}

可以像下面这样调用，其中泛型类型 E 是一个有界类型

and it can be called like below, where the generic type E is a bounded type

class Test<E extends DeepCloneable> {

    public void testDeepClone(E arg) {
        E e = (E) arg.deepClone();
    }
}

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