【死记硬背】

总共有四种，分别是直接赋值拷贝、浅拷贝、深拷贝和序列化。

直接赋值拷贝：这个实际上复制的是对象的引用地址，如：Person p1 = p2，则p1和p2指向的是同一个对象的地址。因此，p1属性变化的时候，p2的属性也会跟着变化。

浅拷贝：复制引用但不复制引用的对象，如果对象的字段是值类型的，那么对该字段执行复制，如果该字段是引用类型的话，则复制引用但不复制引用的对象。

深拷贝：不仅复制对象本身，而且复制对象包含的引用指向的所有对象。

序列化：对象实现Serializable接口，然后将对象写到流中，再从流中读出来，再重建对象。

【答案解析】

直接赋值拷贝

public class Person{
    private String name;
    private int age;
    private Address address;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public Address getAddress() {
        return address;
    }
    public void setAddress(Address address) {
        this.address = address;
    }
    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", address=" + address +
                '}';
    }
}

public class Address{
    private String home;
    public String getHome() {
        return home;
    }
    public void setHome(String home) {
        this.home = home;
    }
    @Override
    public String toString() {
        return "Address{" +
                "home='" + home + '\'' +
                '}';
    }
}

public class Test{
    public static void main(String[] args) {
        Address address = new Address();
        address.setHome("浙江省杭州市");
        Person person = new Person();
        person.setName("面试题解析");
        person.setAge(20);
        person.setAddress(address);
        Person person2 = person;
        System.out.println("person年龄变化前："+person2);
        person.setAge(22);
        System.out.println("person年龄变化后："+person2);
    }
}
// 输出如下
person年龄变化前：Person{name='面试题解析', age=20, address=Address{home='浙江省杭州市'}}
person年龄变化后：Person{name='面试题解析', age=22, address=Address{home='浙江省杭州市'}}

浅拷贝

public class Person implements Cloneable{
    private String name;
    private int age;
    private Address address;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public Address getAddress() {
        return address;
    }
    public void setAddress(Address address) {
        this.address = address;
    }
    @Override
    protected Object clone() throws CloneNotSupportedException{
        try{
            Object o = super.clone();
            Person p = (Person)o;
            return p;
        }catch (Exception e){
            e.printStackTrace();
        }
        return null;
    }
    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", address=" + address +
                '}';
    }
}

深拷贝

public class Person implements Cloneable{
    private String name;
    private int age;
    private Address address;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public Address getAddress() {
        return address;
    }
    public void setAddress(Address address) {
        this.address = address;
    }
    @Override
    protected Object clone() throws CloneNotSupportedException{
        try{
            Object o = super.clone();
            Person p = (Person)o;
            Object address = this.address.clone();
            p.setAddress((Address) address);
            return p;
        }catch (Exception e){
            e.printStackTrace();
        }
        return null;
    }
    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", address=" + address +
                '}';
    }
}

序列化

特点必须实现Serialable接口，使用ObjectInputStream和ObjectOutputStream两个类来实现复制拷贝功能(序列化和反序列化)。

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