Java的克隆与C+的拷贝之间的区别

Java的克隆与C+的拷贝之间的区别

有的人会误认两者是同样的东西，Java有深克隆、浅克隆，C+有深拷贝、浅拷贝，这里为大家详细介绍一下两者的区别。

首先带着大家复习一下C+中深拷贝和浅拷贝的区别

在对一个对象进行拷贝时，拷贝的结果仅仅是将这个对象的地址赋给拷贝对象，在对拷贝对象进行修改的时候，原对象也会做出相应的改变，这就是浅拷贝。
为了拷贝能得到一个地址不一样的新的对象，需要重写拷贝构造函数，创建一个新的对象一一赋值再返回，这就是深拷贝。

C+中可以通过重载运算符完成深拷贝，Java中没有运算符重载该如何完成深拷贝呢？

Java中提供了clone方法来完成深拷贝的功能，但是clone也分为深克隆和浅克隆。分别是怎么实现的下面通过两个例子为大家讲解。
对象要实现克隆首先要继承clonable的接口，然后重写clone方法。

浅克隆

浅克隆得到的对象与原对象的地址不同，但是成员变量为基本数据类型的时候，直接赋值给克隆对象，成员变量为引用类型的时候，会把该引用类型的地址赋给克隆对象。也就是 对象完成了深拷贝，但是对象中的对象还是浅拷贝。

public class Main{
	public static void main(String[] args) throws Exception {
		Pet pet = new Pet("xiaohuang","dog");
		Person person1 = new Person(pet, "zhangsan");
		Person person2 = (Person)person1.clone();
		person2.getPet().setType("cat");
		System.out.println(person1);
		System.out.println(person2);
	}
}

class Person implements Cloneable{
	private Pet pet;
	private String name;
	public Person(Pet pet,String name) {
		// TODO Auto-generated constructor stub
		this.pet = pet;
		this.name = name;
	}
	@Override
	public Object clone() throws CloneNotSupportedException {
		// TODO Auto-generated method stub
		return super.clone();
	}
	@Override
	public String toString() {
		// TODO Auto-generated method stub
		return"name = " + name + ", pet[" + pet.toString() + "]";
	}
	public Pet getPet() {
		return pet;
	}
	public void setPet(Pet pet) {
		this.pet = pet;
	}
	public String getName() {
		return name;
		}
	public void setName(String name) {
		this.name = name;
		}
}
class Pet implements Cloneable{
	private String nickname;
	private String type;
	public Pet(String nickname,String type) {
		// TODO Auto-generated constructor stub
		this.nickname = nickname;
		this.type = type;
	}
	@Override
	protected Object clone() throws CloneNotSupportedException {
		// TODO Auto-generated method stub
		return super.clone();
	}
	public String getNickname() {
		return nickname;
	}
	public void setNickname(String nickname) {
		this.nickname = nickname;
	}
	public String getType() {
		return type;
	}
	public void setType(String type) {
		this.type = type;
	}
	@Override
	public String toString() {
		// TODO Auto-generated method stub
		return "nickname =" + nickname + ",type = " + type;
	}
}

运行结果如下：

name = zhangsan, pet[nickname =xiaohuang,type = cat]
name = lisi, pet[nickname =xiaohuang,type = cat]

深克隆

深克隆的实现也很简单，重载对象的clone即可。

public class Main{
	public static void main(String[] args) throws Exception {
		Pet pet = new Pet("xiaohuang","dog");
		Person person1 = new Person(pet, "zhangsan");
		Person person2 = (Person)person1.clone();
		person2.getPet().setType("cat");
		person2.setName("lisi");
		System.out.println(person1);
		System.out.println(person2);
	}
}

class Person implements Cloneable{
	private Pet pet;
	private String name;
	public Person(Pet pet,String name) {
		// TODO Auto-generated constructor stub
		this.pet = pet;
		this.name = name;
	}
	@Override
	public Object clone() throws CloneNotSupportedException {
		// TODO Auto-generated method stub
		Person person = (Person)super.clone();
		person.setPet((Pet)this.pet.clone());
		return person;
	}
	@Override
	public String toString() {
		// TODO Auto-generated method stub
		return"name = " + name + ", pet[" + pet.toString() + "]";
	}
	public Pet getPet() {
		return pet;
	}
	public void setPet(Pet pet) {
		this.pet = pet;
	}
	public String getName() {
		return name;
		}
	public void setName(String name) {
		this.name = name;
		}
}
class Pet implements Cloneable{
	private String nickname;
	private String type;
	public Pet(String nickname,String type) {
		// TODO Auto-generated constructor stub
		this.nickname = nickname;
		this.type = type;
	}
	@Override
	protected Object clone() throws CloneNotSupportedException {
		// TODO Auto-generated method stub
		return super.clone();
	}
	public String getNickname() {
		return nickname;
	}
	public void setNickname(String nickname) {
		this.nickname = nickname;
	}
	public String getType() {
		return type;
	}
	public void setType(String type) {
		this.type = type;
	}
	@Override
	public String toString() {
		// TODO Auto-generated method stub
		return "nickname =" + nickname + ",type = " + type;
	}
}

运行结果

name = zhangsan, pet[nickname =xiaohuang,type = dog]
name = lisi, pet[nickname =xiaohuang,type = cat]

通过对结果的观察，就会发现已经实现了深克隆。在用到clone方法的时候要多注意噢