对象的克隆/拷贝

通过Object类中的clone()方法 可以克隆出一个对象
protected native Object clone() throws CloneNotSupportedException;

想克隆必须要实现Cloneable接口（不然运行时会抛出CloneNotSupportedException异常）
然后重写clone方法，不然实现类无法直接调用clone()方法（因为protected修饰的）

根据克隆得到的对象分为 深克隆和浅克隆 / 深拷贝和浅拷贝

浅克隆
只克隆对象本身 不克隆对象中所引用的其他对象
Student类：

public class Student implements Cloneable{
    private String name;
    private int age;
    private Teacher teacher;
    public Student(String name, int age, Teacher teacher) {
        this.name = name;
        this.age = age;
        this.teacher = teacher;
    }
    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 Teacher getTeacher() {
        return teacher;
    }
    public void setTeacher(Teacher teacher) {
        this.teacher = teacher;
    }
    @Override
    public Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}

Teacher类：

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.ReentrantReadWriteLock;
public class Teacher{
    private String name;
    private int age;
    public Teacher(String name, int age) {
        this.name = name;
        this.age = age;
    }
    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;
    }
}

深克隆
既克隆对象本身 又克隆对象中所引用的其他对象
Student类：

public class Student implements Cloneable{
    private String name;
    private int age;
    private Teacher teacher;
    public Student(String name, int age, Teacher teacher) {
        this.name = name;
        this.age = age;
        this.teacher = teacher;
    }
    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 Teacher getTeacher() {
        return teacher;
    }
    public void setTeacher(Teacher teacher) {
        this.teacher = teacher;
    }
    @Override
    public Object clone() throws CloneNotSupportedException {
        //深克隆  同时克隆Teacher 得到了一个新的Teacher对象 该对象的引用和原有Student对象中的Teacher引用已经不是同一个了
        Student cloneStudent = (Student) super.clone();
        Teacher cloneTeacher = (Teacher) cloneStudent.getTeacher().clone();
        cloneStudent.setTeacher(cloneTeacher);
        return cloneStudent;
    }
}

Teacher类：

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.locks.ReentrantReadWriteLock;
public class Teacher implements Cloneable{
    private String name;
    private int age;
    public Teacher(String name, int age) {
        this.name = name;
        this.age = age;
    }
    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;
    }
    @Override
    public Object clone() throws CloneNotSupportedException{
        return super.clone();
    }
}

主函数：

public class TestMain {
    public static void main(String[] args) throws CloneNotSupportedException {
        Teacher teacher = new Teacher("zhangsan", 18);
        Student student = new Student("lisi", 16, teacher);
        Student cloneStudent = (Student) student.clone();
        System.out.println(cloneStudent.getName());
        System.out.println(cloneStudent.getAge());
        System.out.println(cloneStudent.getTeacher().getName());
        System.out.println(cloneStudent.getTeacher().getAge());
        // 更改克隆对象 的老师名字和年纪
        cloneStudent.getTeacher().setName("zzt");
        cloneStudent.getTeacher().setAge(17);
        // 查看 原对象 的老师名字和年纪  是否被更改
        System.out.println(student.getTeacher().getName());
        System.out.println(student.getTeacher().getAge());
    }
}

浅克隆结果：

此时得到的对象与原对象都引用了同一个Teacher对象 即为浅克隆
深克隆结果：

此时得到的对象与原对象引用的不是同一个Teacher对象 即为深克隆