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Java对象深拷贝与浅拷贝的区别

news 来源：原创 2025/6/18 12:50:59

一、浅拷贝

浅拷贝是指创建一个新对象，并将原对象的字段值复制到新对象中。如果字段是基本数据类型，则直接复制其值；如果字段是引用类型，则复制的是引用（即两个对象的引用字段指向同一个内存地址）。

示例代码

class Address {
    String street;
    String city;

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

class Person {
    String name;
    Address address;

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

public class ShallowCopyExample {
    public static void main(String[] args) {
        Address originalAddress = new Address("123 Main St", "Anytown");
        Person originalPerson = new Person("John Doe", originalAddress);

        // 浅拷贝
        Person copiedPerson = new Person(originalPerson.name, originalPerson.address);

        // 修改拷贝对象的地址
        copiedPerson.address.city = "New City";

        System.out.println("Original person's address: " + originalPerson.address.city);
        System.out.println("Copied person's address: " + copiedPerson.address.city);
    }
}

输出结果

Original person's address: New City
Copied person's address: New City

代码解析

在上述代码中，copiedPerson 是通过浅拷贝创建的。它复制了 originalPerson 的 name 字段和 address 引用。由于 address 是引用类型，两个 Person 对象的 address 字段指向同一个 Address 对象。因此，当修改 copiedPerson 的地址时，originalPerson 的地址也会发生变化。

二、深拷贝

深拷贝是指创建一个新对象，并将原对象的字段值复制到新对象中。如果字段是引用类型，则递归地创建该引用对象的深拷贝，确保新对象与原对象在内存中完全独立。

示例代码

class Address implements Cloneable {
    String street;
    String city;

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

    @Override
    public Address clone() {
        try {
            return (Address) super.clone();
        } catch (CloneNotSupportedException e) {
            throw new AssertionError();
        }
    }
}

class Person implements Cloneable {
    String name;
    Address address;

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

    @Override
    public Person clone() {
        try {
            Person cloned = (Person) super.clone();
            cloned.address = address.clone();
            return cloned;
        } catch (CloneNotSupportedException e) {
            throw new AssertionError();
        }
    }
}

public class DeepCopyExample {
    public static void main(String[] args) {
        Address originalAddress = new Address("123 Main St", "Anytown");
        Person originalPerson = new Person("John Doe", originalAddress);

        // 深拷贝
        Person copiedPerson = originalPerson.clone();

        // 修改拷贝对象的地址
        copiedPerson.address.city = "New City";

        System.out.println("Original person's address: " + originalPerson.address.city);
        System.out.println("Copied person's address: " + copiedPerson.address.city);
    }
}

输出结果

Original person's address: Anytown
Copied person's address: New City

代码解析

在上述代码中，copiedPerson 是通过深拷贝创建的。它复制了 originalPerson 的 name 字段，并创建了 address 对象的深拷贝。因此，两个 Person 对象的 address 字段指向不同的 Address 对象。修改 copiedPerson 的地址不会影响 originalPerson 的地址。