用一个已经创建的实例作为原型，通过复制该原型对象来创建一个和原型相同或相似的新对象。在这里，原型实例指定了要创建的对象的种类。用这种方式创建对象非常高效，根本无须知道对象创建的细节。

package com.strife.pattern.prototype;

import java.io.*;

/**
 * 原型模式
 *
 * @author mengzhenghao
 * @date 2022/5/29
 */
public class Prototype {

    public static void main(String[] args) throws IOException, ClassNotFoundException {
        final Sheep sheep = new Sheep("sheep", 1, "白色");
        System.out.println(sheep);
        final Sheep dolly = sheep.clone();
        System.out.println(dolly);

        final Sheep dolly1 = sheep.deepClone();
        System.out.println(dolly1);
        final Sheep dolly2 = sheep.deepClone2();
        System.out.println(dolly2);
    }
}

class Cat implements Cloneable, Serializable {
    private String name;

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

    @Override
    public Cat clone() {
        try {
            Cat clone = (Cat) super.clone();
            // TODO: copy mutable state here, so the clone can't change the internals of the original
            return clone;
        } catch (CloneNotSupportedException e) {
            throw new AssertionError();
        }
    }
}

class Sheep implements Cloneable, Serializable {
    private String name;
    private int age;
    private String color;
    public Cat friend;

    public Sheep(String name, int age, String color) {
        this.name = name;
        this.age = age;
        this.color = color;
        this.friend = new Cat("friend");
    }

    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 String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    @Override
    public String toString() {
        return "Sheep{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", color='" + color + '\'' +
                ", friend=" + friend.hashCode() +
                '}';
    }

    /**
     * 浅拷贝，默认为浅拷贝
     * Sheep{name='sheep', age=1, color='白色', friend=325040804}
     * Sheep{name='sheep', age=1, color='白色', friend=325040804}
     */
    @Override
    public Sheep clone() {
        try {
            Sheep clone = (Sheep) super.clone();
            return clone;
        } catch (CloneNotSupportedException e) {
            throw new AssertionError();
        }
    }

    /**
     * 深拷贝，引用对象单独拷贝
     * Sheep{name='sheep', age=1, color='白色', friend=325040804}
     * Sheep{name='sheep', age=1, color='白色', friend=1173230247}
     */
    //@Override
    //public Sheep clone() {
    //    try {
    //        Sheep clone = (Sheep) super.clone();
    //        clone.friend = this.friend.clone();
    //        return clone;
    //    } catch (CloneNotSupportedException e) {
    //        throw new AssertionError();
    //    }
    //}

    /**
     * 深拷贝
     * Sheep{name='sheep', age=1, color='白色', friend=325040804}
     * Sheep{name='sheep', age=1, color='白色', friend=1915910607}
     */
    public Sheep deepClone() {
        ByteArrayOutputStream bos = null;
        ObjectOutputStream oos = null;
        ByteArrayInputStream bis = null;
        ObjectInputStream ois = null;

        try {
            bos = new ByteArrayOutputStream();
            oos = new ObjectOutputStream(bos);
            //将对象写到流里面：序列化
            oos.writeObject(this);
            bis = new ByteArrayInputStream(bos.toByteArray());
            ois = new ObjectInputStream(bis);
            //从流里面读出对象：反序列化
            return (Sheep) ois.readObject();
        } catch (IOException | ClassNotFoundException e) {
            throw new RuntimeException(e.getMessage());
        } finally {
            if (ois != null) {
                try {
                    ois.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (bis != null) {
                try {
                    bis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (oos != null) {
                try {
                    oos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (bos != null) {
                try {
                    bos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    /**
     * try with resources
     * Sheep{name='sheep', age=1, color='白色', friend=325040804}
     * Sheep{name='sheep', age=1, color='白色', friend=284720968}
     */
    public Sheep deepClone2() {

        try (
                ByteArrayOutputStream bos = new ByteArrayOutputStream();
                ObjectOutputStream oos = new ObjectOutputStream(bos);
        ) {
            oos.writeObject(this);
            //从流里面读出对象：反序列化
            try (
                    ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
                    ObjectInputStream ois = new ObjectInputStream(bis);
            ) {
                //将对象写到流里面：序列化
                return (Sheep) ois.readObject();
            }
        } catch (IOException | ClassNotFoundException e) {
            throw new RuntimeException(e.getMessage());
        }
    }
}