深拷贝和浅拷贝

引用数据类型是指通过定义一个引用类型的变量，可以指向并操作其他的对象实体，引用存放在栈中，实体存放在堆中。常见的引用数据类型有类（class），接口（interface），数据（array）,字符串（String），包装类（Integer、Float）。浅拷贝和深拷贝都是对于引用数据类型而言。

2、浅拷贝和深拷贝的区别

（1）浅拷贝

浅拷贝是指会创建一个新对象，但是只复制原始对象的基本类型字段或引用，如果原始对象存在引用类型的字段，拷贝对象和原始对象的引用类型字段会共享同一个实体，对拷贝对象的修改可能会影响原始对象。

（2）深拷贝

深拷贝会递归复制原始对象的所有属性和属性指向的实体，拷贝对象和原始对象各自独立，对拷贝对象的修改不会影响原始对象。

示例图参考：澡澡洗澡澡-一文彻底搞懂深拷贝和浅拷贝的区别

二、通过实现Cloneable接口进行拷贝

1、浅拷贝

实体类需要实现Cloneable接口，并重写clone方法

（1）Address类

package com.xiaobai.java_core.copy;

import java.io.Serializable;

/**
 * @Author 王天文
 * @Date 2025/1/5 15:55
 * @Description:
 */
public class Address implements Serializable, Cloneable {

    private static final long serialVersionUID = -2017435981055252655L;

    public Address(String city) {
        this.city = city;
    }

    private String city;

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    @Override
    protected Address clone() throws CloneNotSupportedException {
        return (Address) super.clone();
    }

    @Override
    public String toString() {
        return "Address{" +
                "city='" + city + '\'' +
                '}';
    }
}

（2）Person类

package com.xiaobai.java_core.copy;

import java.io.Serializable;

/**
 * @Author 王天文
 * @Date 2025/1/5 15:54
 * @Description:
 */
public class Person implements Serializable, Cloneable {

    private static final long serialVersionUID = 7973985896659216593L;

    public Person() {
    }

    public Person(String name, String sex, Address address) {
        this.name = name;
        this.sex = sex;
        this.address = address;
    }

    private String name;

    private String sex;

    private Address address;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    /**
     * 浅拷贝
     * @return
     * @throws CloneNotSupportedException
     */
    @Override
    protected Person clone() throws CloneNotSupportedException {
        Person personClone = (Person) super.clone();
        return personClone;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", address=" + address +
                '}';
    }
}

（3）测试代码

package com.xiaobai.java_core.copy;

import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.Test;

/**
 * @Author 王天文
 * @Date 2025/1/5 18:32
 * @Description: 浅拷贝和深拷贝测试
 */
@Slf4j
public class CopyTest {

    @Test
    public void shallowCopy() throws CloneNotSupportedException {
        Person person = new Person("张三", "男", new Address("北京"));

        Person personCopy = person.clone();

        personCopy.getAddress().setCity("上海");

        log.info("原始对象：" + person);
        log.info("拷贝对象：" + personCopy);
    }
}

（4）输出

原始对象：Person{name='张三', sex='男', address=Address{city='上海'}}
拷贝对象：Person{name='张三', sex='男', address=Address{city='上海'}}

可以看到对拷贝对象的修改影响了原始对象，person对象和personCopy对象的address属性的堆内存是共享的。

2、深拷贝

在Person类中添加deepClone方法，在拷贝Person对象的同时也拷贝成员变量address，并赋值给Person的拷贝对象。Address类的代码不变。

（1）Person类代码修改

package com.xiaobai.java_core.copy;

import java.io.Serializable;

/**
 * @Author 王天文
 * @Date 2025/1/5 15:54
 * @Description:
 */
public class Person implements Serializable, Cloneable {

    private static final long serialVersionUID = 7973985896659216593L;

    public Person() {
    }

    public Person(String name, String sex, Address address) {
        this.name = name;
        this.sex = sex;
        this.address = address;
    }

    private String name;

    private String sex;

    private Address address;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    /**
     * 浅拷贝
     * @return
     * @throws CloneNotSupportedException
     */
    @Override
    protected Person clone() throws CloneNotSupportedException {
        Person personClone = (Person) super.clone();
        return personClone;
    }

    /**
     * 深拷贝
     * @return
     * @throws CloneNotSupportedException
     */
    public Person deepClone() throws CloneNotSupportedException {
        Person personClone = (Person) super.clone();
        personClone.address = this.address.clone();
        return personClone;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", address=" + address +
                '}';
    }
}

（2）测试代码

    @Test
    public void deepCopy() throws CloneNotSupportedException {
        Person person = new Person("张三", "男", new Address("北京"));

        Person personCopy = person.deepClone();

        personCopy.getAddress().setCity("上海");

        log.info("原始对象：" + person);
        log.info("拷贝对象：" + personCopy);
    }

（3）输出

原始对象：Person{name='张三', sex='男', address=Address{city='北京'}}

拷贝对象：Person{name='张三', sex='男', address=Address{city='上海'}}

三、浅拷贝和深拷贝工具类

1、浅拷贝

（1）示例代码

使用Spring的org.springframework.beans.BeanUtils#copyProperties(java.lang.Object, java.lang.Object)可以实现浅拷贝

package com.xiaobai.java_core.copy;

import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.Test;
import org.springframework.beans.BeanUtils;

/**
 * @Author 王天文
 * @Date 2025/1/5 19:48
 * @Description:
 */
@Slf4j
public class SpringCopyTest {

    @Test
    public void shallowCopy() {
        Person person = new Person("张三", "男", new Address("北京"));

        Person personCopy = new Person();

        BeanUtils.copyProperties(person, personCopy);

        personCopy.getAddress().setCity("上海");

        log.info("原始对象：" + person);
        log.info("拷贝对象：" + personCopy);
    }
}

（2）输出

原始对象：Person{name='张三', sex='男', address=Address{city='上海'}}

拷贝对象：Person{name='张三', sex='男', address=Address{city='上海'}}

2、深拷贝

（1）示例代码

使用org.apache.commons.lang.SerializationUtils实现深拷贝，示例代码如下：

    @Test
    public void deepCopy() {
        Person person = new Person("张三", "男", new Address("北京"));

        // 使用SerializationUtils进行深拷贝
        Person personCopy = (Person) SerializationUtils.clone(person);

        personCopy.getAddress().setCity("上海");

        log.info("原始对象：" + person);
        log.info("拷贝对象：" + personCopy);
    }