Java的深克隆的浅克隆

Java的深克隆的浅克隆

1、浅拷贝和深拷贝

• 浅拷贝：复制的是目标对象，目标对象的引用并不会复制，还是原来的引用
• 深拷贝：复制的是目标对象以及目标对象中的引用对象。

2、clone方法

• 在Java的Object对象中，有clone这个方法。它被声明为了 protected，所以我们可以在其子类中使用它。这里需要注意的是，我们在子类中使用clone方法时，子类需要实现Cloneable接口，否则会抛出java.lang.CloneNotSupportedException异常。

3、浅拷贝实现代码

@Data
public class Person implements Cloneable{

    private String name;

    private Integer age;

    private Address address;

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

@Data
public class Address {

    private String name;
}


public class Client {

    public static void main(String[] args) throws      				CloneNotSupportedException {
        Address address = new Address();
        address.setName("浙江省杭州市");
        Person person = new Person();
        person.setAge(23);
        person.setName("joker");
        person.setAddress(address);
        Person copy = (Person) person.clone();
        System.out.println(copy == person);			     System.out.println(copy.getAddress()==person.getAddress());
        address.setName("宁波");
        System.out.println(person.getAddress().toString());
        System.out.println(copy.getAddress().toString());
    }
}

结果：
false
true
Address(name=宁波)
Address(name=宁波)

4、浅拷贝存在的问题

• 当拷贝的目标对象中，存在别的引用对象，例如Person中存在Address的引用。如果修改address的属性的话，拷贝兑现的address的属性也会被改变

5、深拷贝的实现

• clone

  @Data
  public class Address implements Cloneable{
  
      private String name;
  
      @Override
      protected Object clone() throws CloneNotSupportedException {
          return super.clone();
      }
  }
  
  public static void main(String[] args) throws CloneNotSupportedException {
          Address address = new Address();
          address.setName("浙江省杭州市");
          Person person = new Person();
          person.setAge(23);
          person.setName("joker");
          person.setAddress(address);
          Person copy = (Person) person.clone();
          copy.setAddress((Address) person.getAddress().clone());
          System.out.println(copy == person);
          System.out.println(copy.getAddress()==person.getAddress());
          address.setName("宁波");
          System.out.println(person.getAddress().toString());
          System.out.println(copy.getAddress().toString());
      }
  
  结果：
  false
  true
  Address(name=宁波)
  Address(name=浙江省杭州市)
  

• 序列化

  public class Client {
  
      public static void main(String[] args) throws CloneNotSupportedException {
          Address address = new Address();
          address.setName("浙江省杭州市");
          Person person = new Person();
          person.setAge(23);
          person.setName("joker");
          person.setAddress(address);
          byte[] serial = SerializationUtils.serialize(person);
          Person copy = (Person) SerializationUtils.deserialize(serial);
          System.out.println(copy == person);
          System.out.println(copy.getAddress()==person.getAddress());
          address.setName("宁波");
          System.out.println(person.getAddress().toString());
          System.out.println(copy.getAddress().toString());
      }
  }
  

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