Java中的Clone() [英] Clone() in java

问题描述

import java.util.*;
import java.lang.*;

public class Test{
    public static void main(String[] argv){
        String s1="abc";
        String s2=(String) s1.clone();
    }    
}

为什么这个简单的测试程序不起作用?

Why this simple test program doesn't work?

推荐答案

clone 是Object类的一种方法.为了使一个类可克隆"，它应该实现标记 Cloneable 接口. String 类无法实现此接口，并且不会覆盖clone方法，因此会导致错误.

clone is a method of the Object class. For a class to be "cloneable" it should implement the marker Cloneable interface. String class doesn't implement this interface and doesn't override the clone method hence the error.

我希望上面的代码段是出于教育目的，因为鉴于以下情况，您永远不会觉得需要在Java字符串中调用 clone :

I hope the above snippet is for educational purposes because you should never feel a need to call clone on strings in Java given that:

1. Java中的字符串是不可变的.随时在方法/类之间共享它们
2. 已经存在一个构造函数 new String(String)，其作用类似于复制构造函数，几乎等效于您的 clone()调用.

1. Strings in Java are immutable. Feel free to share them across methods/classes
2. There already exists a constructor new String(String) which acts like a copy constructor and is pretty much equivalent to your clone() call.

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