回答重点
深拷贝：深拷贝不仅复制对象本身，还递归复制对象中所有引用的对象。这样新对象与原对象完全独立，修改新对象不会影响到原对象。即包括基本类型和引用类型，堆内的引用对象也会复制一份
浅拷贝：浅拷贝只复制对象的引用，而不复制引用指向的实际对象，也就是说，浅拷贝创建一个新对象，但它的字段（若是对象类型）指向的是原对象中的相同内存地址
深拷贝创建的新对象与原对象完全独立，任何一个对象的修改都不会影响另一个。二修改浅拷贝对象中的引用类型的字段会影响要原对象，因为它们共享相同的引用
扩展知识
图示深浅拷贝
浅拷贝实现
常见实现方式是重写Object.clone()方法，默认方法这个方法只是对对象的字段进行字段拷贝，对于基本类型的字段会复制值，对于引用类型的字段则复制引用
重写Clone()的类需要实现Cloneable接口，否则抛出异常CloneNotSupportedException
public class ShallowCopyTest {public static void main(String[] args) throws CloneNotSupportedException{ShallowCopyTest test = new ShallowCopyTest();Person john = test.new Person("John", 25, new ArrayList<>(Arrays.asList("电玩", "旅游")));Person johnCopy = (Person) john.clone();System.out.println(john);System.out.println(johnCopy);System.out.println(john.hobbies == johnCopy.hobbies);}class Person implements Cloneable{String name;int age;List<String> hobbies;public Person(String name, int age, List<String> hobbies) {this.name = name;this.age = age;this.hobbies = hobbies;}@Overrideprotected Object clone() throws CloneNotSupportedException {return super.clone();}@Overridepublic String toString(){return name + "已经" + age + "岁了，喜欢" + hobbies.get(0) + " 和 " + hobbies.get(1);}}
}
深拷贝实现
深拷贝可以通过递归调用clone()方法手动实现，也可以通过序列化与反序列化实现。序列化方式简单易用，但性能相对较低，尤其是在深层嵌套对象或大对象的情况下。
- 递归调用clone()实现
public class DeepCopyTest {public static void main(String[] args) throws CloneNotSupportedException {DeepCopyTest test = new DeepCopyTest();People people = test.new People("Autism", 21, test.new Address("HeFei"));People clone = (People) people.clone();System.out.println(people.address == clone.address);}class People implements Cloneable{String name;int age;Address address;public People(String name, int age, Address address) {this.name = name;this.age = age;this.address = address;}@Overrideprotected Object clone() throws CloneNotSupportedException {People p = (People) super.clone(); // 先浅拷贝p.address = (Address) address.clone(); // 引用字段手动拷贝return p;}}class Address implements Cloneable{String city;public Address(String city){this.city = city;}@Overrideprotected Object clone() throws CloneNotSupportedException {return super.clone();}}
}
- 序列化实现
public static Object deepCopy(Object object) {try {ByteArrayOutputStream bos = new ByteArrayOutputStream();ObjectOutputStream oos = new ObjectOutputStream(bos);oos.writeObject(object);ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());ObjectInputStream ois = new ObjectInputStream(bis);return ois.readObject();} catch (Exception e) {e.printStackTrace();return null;}
}