原型模式

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原型模式：
用原型实例指定创建对象的种类，并且通过拷贝这些原型创建新的对象。
类图：
这里写图片描述

原型模式主要用于对象的复制，其核心是Prototype类。JAVA中Prototype类具备以下两个条件：
- 实现Cloneable接口。JAVA中有一个Cloneable接口，作用是通知虚拟机可以安全的在实现了此接口的类上使用clone方法。在JAVA中，只有实现了Cloneable才能使用clone方法进行拷贝，否则会抛出CloneNotSupportedException异常。
- 重写Clone方法。Clone方法是Object中的方法，作用是返回对象的一个拷贝，但其作用域一般是protected，一般的类无法调用，因此Prototype需要把clone方法改成public修饰。

浅复制与深复制：
现在已要写一份简历类，简历包括姓名，性别，包括一个工作经历类，工作经历类包括工作时间和公司信息。然后拷贝简历三份。

浅赋值代码如下：

// 工作经历类public class WorkExperience {    public String workDate;    public String company;    public void setWorkDate(String workDate){        this.workDate = workDate;    }    public String getWorkDate(){        return workDate;    }    public void setCompany(String company){        this.company = company;    }    public String getCompany(){        return company;    }}// 简历类    private String name;    private String age;    private String sex;    private WorkExperience workExperience;    public Resume(String name){        this.name = name;        workExperience = new WorkExperience();    }    // 设置个人信息    public void SetPersonalInfo(String sex,             String age){        this.age = age;        this.sex = sex;    }    // 设置工作经历    public void SetWorkExperience(String workDate,            String company){        workExperience.workDate = workDate;        workExperience.company = company;    }    //打印    public void Dispaly(){        System.out.println(name + "  " + age+" "+ " "+sex );        System.out.println("工作经历:" + workExperience.workDate + " "+                workExperience.company);    }    // 重写clone方法    @Override    public Resume clone() throws CloneNotSupportedException {        // TODO Auto-generated method stub        Resume resume = null;        try{            resume = (Resume)super.clone();        }catch (CloneNotSupportedException e) {            // TODO: handle exception            e.printStackTrace();        }        return resume;    }}// 客户端    private String name;    private String age;    private String sex;    private WorkExperience workExperience;    public Resume(String name){        this.name = name;        workExperience = new WorkExperience();    }    // 设置个人信息    public void SetPersonalInfo(String sex,             String age){        this.age = age;        this.sex = sex;    }    // 设置工作经历    public void SetWorkExperience(String workDate,            String company){        workExperience.workDate = workDate;        workExperience.company = company;    }    //打印    public void Dispaly(){        System.out.println(name + "  " + age+" "+ " "+sex );        System.out.println("工作经历:" + workExperience.workDate + " "+                workExperience.company);    }    // 重写clone方法    @Override    public Resume clone() throws CloneNotSupportedException {        // TODO Auto-generated method stub        Resume resume = null;        try{            resume = (Resume)super.clone();        }catch (CloneNotSupportedException e) {            // TODO: handle exception            e.printStackTrace();        }        return resume;    }}

以上代码叫做浅复制，被复制对象的所有变量都含有与原来的对象相同的值，而所有的对其他对象的引用都仍然指向原来的对象。也就是说，代码中“工作经历”虽然在resumeA，resumeB，resumeC中分别有复制，但是这三份简历中的引用都指向同一个对象的。

将浅复制改为深复制，代码如下：

// 工作经历类public class WorkExperience implements Cloneable{    public String workDate;    public String company;    public void setWorkDate(String workDate){        this.workDate = workDate;    }    public String getWorkDate(){        return workDate;    }    public void setCompany(String company){        this.company = company;    }    public String getCompany(){        return company;    }    // 重写clone方法    @Override    public WorkExperience clone() throws CloneNotSupportedException {        // TODO Auto-generated method stub        WorkExperience workExperience = null;        try{            workExperience = (WorkExperience) super.clone();        }catch (CloneNotSupportedException e) {            // TODO: handle exception            e.printStackTrace();        }        return workExperience;    }}// 简历类public class Resume implements Cloneable {    private String name;    private String age;    private String sex;    private WorkExperience workExperience;    public Resume(String name){        this.name = name;        workExperience = new WorkExperience();    }    private Resume(WorkExperience workExperience){        this.workExperience = workExperience;    }    // 设置个人信息    public void SetPersonalInfo(String sex,             String age){        this.age = age;        this.sex = sex;    }    // 设置工作经历    public void SetWorkExperience(String workDate,            String company){        workExperience.workDate = workDate;        workExperience.company = company;    }    //打印    public void Dispaly(){        System.out.println(name + "  " + age+" "+ " "+sex );        System.out.println("工作经历:" + workExperience.workDate + " "+                workExperience.company);    }    // 重写clone方法    @Override    public Resume clone() throws CloneNotSupportedException {        // TODO Auto-generated method stub        Resume resume = new Resume(this.workExperience);        resume.name = this.name;        resume.age = this.age;        resume.sex = this.sex;        return resume;    }}// 客户端public class Main {    public static void main(String[] args) {        // TODO Auto-generated method stub        Resume resumeA = new Resume("大磊");        resumeA.SetPersonalInfo("男", "22");        resumeA.SetWorkExperience("2016-2017", "bbk");        resumeA.Dispaly();        Resume resumeB = null;        Resume resumeC = null;        try {            resumeB = (Resume)resumeA.clone();            resumeC = (Resume)resumeA.clone();        } catch (CloneNotSupportedException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        resumeB.Dispaly();        resumeC.Dispaly();    }}

深复制把引用对象的变量指向复制过的新对象，而不是原有的引用对象。

分析：
使用原型模式创建对象比直接new一个对象在性能上要好的多，因为Object类的clone方法是一个本地方法，它直接操作内存中的二进制流，特别是复制大对象时，性能的差别非常明显。

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