原型模式

1、概念
使用原型实例，指定创建对象的种类，并且通过复制这些原型创建新的对象。

2、Cloneable接口

class Professor{    String name;    int age;    Professor(String name, int age) {        this.name = name;        this.age = age;    }}

class Student implements Cloneable {    String name;    int age;    Professor p;// 引用    Student(String name, int age, Professor p) {        this.name = name;        this.age = age;        this.p = p;    }    @Override    public Object clone() {        Student o = null;        try {            o = (Student) super.clone();        } catch (CloneNotSupportedException e) {            System.out.println(e.toString());        }        return o;    }}

public class CloneTest {    public static void main(String[] args) {        Professor p = new Professor("wangwu", 50);        Student s1 = new Student("zhangsan", 18, p);        System.out.println(s1.name + " " + s1.p.name + " " + s1.p.age);        Student s2 = (Student) s1.clone();        // s2的Professor信息        s2.p.name = "lisi";        s2.p.age = 30;        // s2的信息        s2.name = "z";        s2.age = 45;        System.out.println(s1.name + " " + s1.p.name + " " + s1.p.age);    }}

输出：

zhangsan wangwu 50zhangsan lisi 30

发现问题：
改变s1的拷贝对象s2的professor的信息，竟然也改变了s1的professor的信息

1）浅拷贝
对于基本数据类型，copy和原型是相等且独立的，copy的变化不会引起原型的变化；
对于引用数据类型，copy和原型是统一的，即二者指向同一个对象，即堆中的同一块区域。
所以，copy中引用的变化，会引起原型的变化。

2）深拷贝
针对浅拷贝中引用的问题，在clone()函数中，对引用对象手动进行拷贝，解决浅拷贝问题，即深拷贝。

浅拷贝只考虑当前拷贝的对象，不考虑该对象引用的对象；
深拷贝不仅考虑当前的对象，还考虑所有引用的对象。

class Professor implements Cloneable {    String name;    int age;    Professor(String name, int age) {        this.name = name;        this.age = age;    }    public Object clone() {        Object o = null;        try {            o = super.clone();        } catch (CloneNotSupportedException e) {            System.out.println(e.toString());        }        return o;    }}

class Student implements Cloneable {    String name;    int age;    Professor p;    Student(String name, int age, Professor p) {        this.name = name;        this.age = age;        this.p = p;    }    public Object clone() {        Student o = null;        try {            o = (Student) super.clone();        } catch (CloneNotSupportedException e) {            System.out.println(e.toString());        }        o.p = (Professor) p.clone();        return o;    }}

输出：

zhangsan wangwu 50zhangsan wangwu 50