java中关于深拷贝的几种方式

在java里，当我们需要拷贝一个对象时，有两种类型的拷贝：浅拷贝与深拷贝。

• 浅拷贝只是拷贝了源对象的地址，所以源对象的值发生变化时，拷贝对象的值也会发生变化。
• 深拷贝则是拷贝了源对象的所有值，所以即使源对象的值发生变化时，拷贝对象的值也不会改变。

方式1：构造函数深拷贝

package com.lyj.demo.pojo.cloneTest;import lombok.Getter;@Getterpublic class UserConstruct {    private String userName;    private AddressConstruct address;    public UserConstruct() {    }    public UserConstruct(String userName, AddressConstruct address) {        this.userName = userName;        this.address = address;    }    public static void main(String[] args) {        AddressConstruct address = new AddressConstruct("小区1", "小区2");        UserConstruct user = new UserConstruct("小李", address);        // 调用构造函数进行深拷贝        UserConstruct copyUser = new UserConstruct(user.getUserName(), new AddressConstruct(address.getAddress1(), address.getAddress2()));        // 修改源对象的值        user.getAddress().setAddress1("小区3");        // false        System.out.println(user == copyUser);        // false        System.out.println(user.getAddress().getAddress1() == copyUser.getAddress().getAddress1());        // false        System.out.println(user.getAddress().getAddress1().equals(copyUser.getAddress().getAddress1()));        // true        System.out.println(user.getAddress().getAddress2().equals(copyUser.getAddress().getAddress2()));    }}package com.lyj.demo.pojo.cloneTest;import lombok.Getter;import lombok.Setter;@Getter@Setterpublic class AddressConstruct {    private String address1;    private String address2;    public AddressConstruct() {    }    public AddressConstruct(String address1, String address2) {        this.address1 = address1;        this.address2 = address2;    }}

方式2：重载Clone（）方法深拷贝

Object父类有个clone()的拷贝方法，不过它是protected类型的 ，我们需要重写它并修改为public类型，除此之外，子类还需要实现Cloneable接口来告诉JVM这个类上是可以拷贝的。

package com.lyj.demo.pojo.cloneTest;import lombok.Getter;import lombok.Setter;@Setter@Getterpublic class AddressClone implements Cloneable{    private String address1;    private String address2;    public AddressClone() {    }    public AddressClone(String address1, String address2) {        this.address1 = address1;        this.address2 = address2;    }    @Override    protected AddressClone clone() throws CloneNotSupportedException {        return (AddressClone) super.clone();    }}package com.lyj.demo.pojo.cloneTest;import lombok.Getter;import lombok.Setter;@Setter@Getterpublic class UserClone implements Cloneable{    private String userName;    private AddressClone address;    public UserClone() {    }    public UserClone(String userName, AddressClone address) {        this.userName = userName;        this.address = address;    }        @Override    protected UserClone clone() throws CloneNotSupportedException {        // 需要注意的是，super.clone()其实是浅拷贝，        // 所以在重写UserClone类的clone()方法时，address对象需要调用address.clone()重新赋值        UserClone userClone = (UserClone) super.clone();        userClone.setAddress(this.address.clone());        return userClone;    }    public static void main(String[] args) throws CloneNotSupportedException {        AddressClone address = new AddressClone("小区1", "小区2");        UserClone user = new UserClone("小李", address);        UserClone copyUser = user.clone();        user.getAddress().setAddress1("小区3");        // false        System.out.println(user == copyUser);        // false        System.out.println(user.getAddress().getAddress1().equals(copyUser.getAddress().getAddress1()));    }}

需要注意的是，super.clone()其实是浅拷贝，所以在重写User类的clone()方法时，address对象需要调用address.clone()重新赋值。

方式3：Apache Commons Lang序列化方式深拷贝

Java提供了序列化的能力，我们可以先将源对象进行序列化，再反序列化生成拷贝对象。但是，使用序列化的前提是拷贝的类（包括其成员变量）需要实现Serializable接口。

Apache Commons Lang包对Java序列化进行了封装，我们可以直接使用它。

package com.lyj.demo.pojo.cloneTest;import lombok.Getter;import lombok.Setter;import java.io.Serializable;@Getter@Setterpublic class AddressSerializable implements Serializable {    private String address1;    private String address2;    public AddressSerializable() {    }    public AddressSerializable(String address1, String address2) {        this.address1 = address1;        this.address2 = address2;    }}package com.lyj.demo.pojo.cloneTest;import lombok.Getter;import lombok.Setter;import org.apache.commons.lang3.SerializationUtils;import java.io.Serializable;@Getter@Setterpublic class UserSerializable implements Serializable {    private String userName;    private AddressSerializable address;    public UserSerializable() {    }    public UserSerializable(String userName, AddressSerializable address) {        this.userName = userName;        this.address = address;    }    public static void main(String[] args) {        AddressSerializable address = new AddressSerializable("小区1", "小区2");        UserSerializable user = new UserSerializable("小李", address);        UserSerializable copyUser = SerializationUtils.clone(user);        user.getAddress().setAddress1("小区3");        // false        System.out.println(user == copyUser);        // false        System.out.println(user.getAddress().getAddress1().equals(copyUser.getAddress().getAddress1()));    }}

来源地址：https://blog.csdn.net/wsb8233696/article/details/130907780