定义

维基百科上的一段定义：

The prototype pattern is a creational design pattern in software development. It is used when the type of objects to create is determined by a prototypical instance, which is cloned to produce new objects. This pattern is used to:

avoid subclasses of an object creator in the client application, like the abstract factory pattern does.

avoid the inherent cost of creating a new object in the standard way (e.g., using the ‘new’ keyword) when it is prohibitively expensive for a given application.

这段话的大意就是：原型模式就是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。这种设计模式主要用来避免：

1.像抽象工厂模式一样，将子类暴露给客户端。

2.避免创建新的对象所耗费的成本。

原型模式其实就是从一个对象再创建另外一个可定制的对象，而且不需要知道任何创建的细节。

代码

package com.ans;

abstract class Resume implements Cloneable {
    private String name;
    private int Age;

    public Object clone() {
        Object o = null;
        try {
            o = super.clone();

        } catch (CloneNotSupportedException e) {
            e.printStackTrace();
        }
        return o;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return Age;
    }

    public void setAge(int age) {
        Age = age;
    }
}

class MyResume extends Resume {
    public MyResume(String name, int age) {
        setName(name);
        setAge(age);
    }
}


public class Prototype {
    public static void main(String[] args) {
        Resume resume = new MyResume("lixuehan",24);
        Resume newResume = (Resume)resume.clone();
        newResume.setName("leexuehan");
        System.out.println(newResume.getName() + "," + newResume.getAge());
        System.out.println(resume.getName() + "," + resume.getAge());
        System.out.println(resume == newResume);
    }
}

运行结果：

leexuehan,24
lixuehan,24
false

实现原型模式的关键就是拷贝类要实现Cloneable接口，然后实现 clone 方法。

从main函数的测试环节来看，Object 的默认的 clone 方法，实现的是深拷贝。因为最后在修改了名字之后，再打印原来的对象的名字的时候，依然没有变化。

附加：

这里复习下Java中抽象类和接口的区别：https://github.com/leexuehan/leexuehan.github.com/issues/98