JAVA 中对象的赋值是复制对象的引用，即复制引用
public static void main(String[] args) {
User user = new User(1,"asds",18);
User user1 = user;
System.out.println(user);
System.out.println(user1);
}
JAVA 中复制对象(克隆副本，互不影响)
使用 clone() 方法要求被克隆对象实现 Cloneable 接口，修改覆盖的 clone() 方法的修饰符为 public
public class User implements Cloneable {
private Integer id;
private String name;
private Integer age;
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
再测试
public static void main(String[] args) throws CloneNotSupportedException {
User user = new User(1,"asds",18);
User user1 = (User) user.clone();
System.out.println(user);
System.out.println(user1);
}
浅拷贝
public class Address {
private String address;
public class User implements Cloneable {
private Integer id;
private String name;
private Integer age;
private Address address;
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
测试
public static void main(String[] args) throws CloneNotSupportedException {
Address address = new Address("wuhan");
User user = new User(1,"asds",18,address);
User user1 = (User) user.clone();
// System.identityHashCode() 获取对象唯一标识，若对象不重写 hashCode() 则值和 Object.hashCode() 一样
System.out.println(System.identityHashCode(user)+"\t"+user);
System.out.println(System.identityHashCode(user1)+"\t"+user1);
user.getAddress().setAddress("beijing");
System.out.println(user.hashCode()+"\t"+user);
System.out.println(user1.hashCode()+"\t"+user1);
}
只修改 user，但 user1 也被修改
clone() 方法：属性为基本类型拷贝其值，属性为非基本类型拷贝其引用
深拷贝
public class Address implements Cloneable {
private String address;
@Override
public Object clone() throws CloneNotSupportedException {
return super.clone();
}
public class User implements Cloneable {
private Integer id;
private String name;
private Integer age;
private Address address;
@Override
public Object clone() throws CloneNotSupportedException {
Object clone = super.clone();
Object addressClone = ((User) clone).getAddress().clone();
((User) clone).setAddress((Address) addressClone);
return clone;
}
再测试
实现完整的深拷贝，需要被复制对象的继承链、引用链上的每一个对象都实现克隆机制
被克隆的对象的属性都是基本类型，那只需要被克隆类实现 cloneable 接口即可，若对象的属性包含其他非基本类型对象，那么这些非基本类型的对象都需要实现 cloneable 接口