回忆：之前听一个老师提过，学语言就是学关键字，如果把所有的关键字都搞懂了，这门语言你就属于很熟悉了（很赞同这句话）。
实现Cloneable这个标记接口，重写Object的clone方法，完成拷贝功能
拷贝分为浅拷贝和深拷贝
如果拷贝的对象中的属性都是基本类型，使用浅拷贝就行，如果拷贝的对象中含有引用类型，就需要实现深拷贝
注意：实现深拷贝时，引用对象也要重写clone方法，如果引用对象是继承其他对象的话，上级对象也要重写clone方法。

对象

package com.example.java8.model.copy;
import java.math.BigDecimal;

public class Dog implements Cloneable {

    private Integer id;

    private String name;

    private BigDecimal weight;

    private Food food;

    public Dog(Integer id, String name, BigDecimal weight) {
        this.id = id;
        this.name = name;
        this.weight = weight;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public BigDecimal getWeight() {
        return weight;
    }

    public void setWeight(BigDecimal weight) {
        this.weight = weight;
    }

    public Food getFood() {
        return food;
    }

    public void setFood(Food food) {
        this.food = food;
    }

    @Override
    public String toString() {
        return "Dog{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", weight=" + weight +
                ", food=" + food +
                '}';
    }

    // 浅拷贝(使用时两者选其一)
    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }

    // 深拷贝(使用时两者选其一)
    @Override
    protected Object clone() throws CloneNotSupportedException {
        Object object = super.clone();
        Food food = ((Dog) object).getFood();
        ((Dog) object).setFood((Food) food.clone());
        return object;
    }
}

引用对象

package com.example.java8.model.copy;

public class Food implements Cloneable {

    private String name;

    public Food(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Food{" +
                "name='" + name + '\'' +
                '}';
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}

测试方法

package com.example.java8.model.copy;
import org.junit.Test;
import java.math.BigDecimal;

public class DogTest {

    // 测试浅拷贝
    @Test
    public void test() throws CloneNotSupportedException {
        Dog jack = new Dog(18, "jack", BigDecimal.TEN);
        Dog tom = (Dog) jack.clone();
        tom.setId(19);
        tom.setName("tom");
        tom.setWeight(BigDecimal.ONE);
        System.out.println(jack);
        System.out.println(tom);
    }

    // 测试深拷贝
    @Test
    public void test2() throws CloneNotSupportedException {
        Dog jack = new Dog(18, "jack", BigDecimal.TEN);
        jack.setFood(new Food("冰淇淋"));
        Dog tom = (Dog) jack.clone();
        tom.setId(19);
        tom.setName("tom");
        tom.setWeight(BigDecimal.ONE);
        tom.getFood().setName("三明治");
        System.out.println(jack);
        System.out.println(tom);
    }
}