在Java中,拷贝对象可以通过浅拷贝(Shallow Copy)和深拷贝(Deep Copy)实现。浅拷贝只复制对象的引用,而不复制对象本身。深拷贝则复制对象及其所有引用的对象,创建一个完全独立的副本。
浅拷贝
浅拷贝是指复制对象的引用,而不是对象本身。对于对象内部的引用类型字段,浅拷贝会共享同一个引用。
浅拷贝示例
            
            
              java
              
              
            
          
          class Address implements Cloneable {
    String city;
    Address(String city) {
        this.city = city;
    }
    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
    @Override
    public String toString() {
        return city;
    }
}
class Person implements Cloneable {
    String name;
    int age;
    Address address;
    Person(String name, int age, Address address) {
        this.name = name;
        this.age = age;
        this.address = address;
    }
    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
    @Override
    public String toString() {
        return "Person{name='" + name + "', age=" + age + ", address=" + address + '}';
    }
}
public class ShallowCopyExample {
    public static void main(String[] args) throws CloneNotSupportedException {
        Address address = new Address("New York");
        Person person1 = new Person("John", 25, address);
        Person person2 = (Person) person1.clone();
        System.out.println("Before modifying address:");
        System.out.println("Person 1: " + person1);
        System.out.println("Person 2: " + person2);
        person2.address.city = "San Francisco";
        System.out.println("After modifying address:");
        System.out.println("Person 1: " + person1);
        System.out.println("Person 2: " + person2);
    }
}代码说明
- Address 类 :包含一个 city字段,实现Cloneable接口,并重写clone方法。
- Person 类 :包含 name、age和address字段,实现Cloneable接口,并重写clone方法。
- ShallowCopyExample 类 :展示了浅拷贝的效果。修改 person2的address后,person1的address也会受到影响,因为它们共享同一个Address对象。
深拷贝
深拷贝是指复制对象及其所有引用的对象,创建一个完全独立的副本。对于对象内部的引用类型字段,深拷贝会递归地复制它们。
深拷贝示例
            
            
              java
              
              
            
          
          class Address implements Cloneable {
    String city;
    Address(String city) {
        this.city = city;
    }
    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
    @Override
    public String toString() {
        return city;
    }
}
class Person implements Cloneable {
    String name;
    int age;
    Address address;
    Person(String name, int age, Address address) {
        this.name = name;
        this.age = age;
        this.address = address;
    }
    @Override
    protected Object clone() throws CloneNotSupportedException {
        Person cloned = (Person) super.clone();
        cloned.address = (Address) address.clone();
        return cloned;
    }
    @Override
    public String toString() {
        return "Person{name='" + name + "', age=" + age + ", address=" + address + '}';
    }
}
public class DeepCopyExample {
    public static void main(String[] args) throws CloneNotSupportedException {
        Address address = new Address("New York");
        Person person1 = new Person("John", 25, address);
        Person person2 = (Person) person1.clone();
        System.out.println("Before modifying address:");
        System.out.println("Person 1: " + person1);
        System.out.println("Person 2: " + person2);
        person2.address.city = "San Francisco";
        System.out.println("After modifying address:");
        System.out.println("Person 1: " + person1);
        System.out.println("Person 2: " + person2);
    }
}代码说明
- Address 类 :与浅拷贝示例中相同,实现 Cloneable接口并重写clone方法。
- Person 类 :在 clone方法中,对address字段进行深拷贝(递归调用address的clone方法)。
- DeepCopyExample 类 :展示了深拷贝的效果。修改 person2的address后,person1的address不会受到影响,因为它们拥有独立的Address对象。
通过这些示例代码,可以看到浅拷贝和深拷贝在实现和效果上的差异。浅拷贝会共享对象的引用,而深拷贝则创建独立的对象副本。