Java学习笔记——设计模式之六.原型模式（浅克隆和深克隆）

That there's some good in this world, Mr. Frodo. And it's worth fighting for.

原型模式（prototype），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。

至于Object.clone()这里就不赘述了。文档看起来可能有些难懂，直接上代码反而更容易理解：

浅克隆：

 package cn.happy.design_pattern._06prototype.shallowclone;

 public abstract class Prototype {

     private String id;

     String getId() {
         return id;
     }

     void setId(String id) {
         this.id = id;
     }

     public abstract Prototype mClone();
 }

 package cn.happy.design_pattern._06prototype.shallowclone;

 public class ConcretePrototype extends Prototype implements Cloneable{

     private Obj obj;
     public ConcretePrototype() {
         super();
         obj = new Obj();
     }

     /*
      * getter and setter
      */
     Obj getObj() {
         return obj;
     }

     void setObj(Obj obj) {
         this.obj = obj;
     }

     @Override
     public Prototype mClone() {
         // TODO Auto-generated method stub
         Prototype prototype = null;
         try {
             prototype = (Prototype)this.clone();
         } catch (CloneNotSupportedException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         return prototype;
     }

 }

 package cn.happy.design_pattern._06prototype.shallowclone;

 public class Obj {

     private String name;

     String getName() {
         return name;
     }

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

 }

 package cn.happy.design_pattern._06prototype.shallowclone;

 public class Mmain {

     public static void main(String[] args) {
         ConcretePrototype c1 = new ConcretePrototype();
         ConcretePrototype c2 = (ConcretePrototype)c1.mClone();
         c1.setId("原型");
         c1.getObj().setName("张三");
         c2.setId("副本");
         c2.getObj().setName("李四");
         /*
          *  浅克隆：
          *  Id是值类型变量，逐位复制，产生新的变量地址；Obj是引用变量，只复制引用，副本和原型共享同一变量地址；
          *  输出：prototype.shallowclone.ConcretePrototype@15db9742,原型,李四
          *       prototype.shallowclone.ConcretePrototype@6d06d69c,副本,李四
          */
         System.out.println(c1+","+c1.getId()+","+c1.getObj().getName());
         System.out.println(c2+","+c2.getId()+","+c2.getObj().getName());

     }

 }

这里需要提下两种特殊的值类型变量，字符串（其实字符串底层是char数组）和数组。它们虽然是引用类型但是可被浅克隆。大家一试便知。

深克隆：

Prototype 类不变。

 package cn.happy.design_pattern._06prototype.deepclone;

 public class ConcretePrototype extends Prototype implements Cloneable{

     private Obj obj;
     public ConcretePrototype() {
         super();
         obj = new Obj();
     }
     //添加新的构造方法
     private ConcretePrototype(Obj obj) {
         super();
         this.obj = (Obj) obj.mClone();
     }

     /*
      * getter and setter
      */
     Obj getObj() {
         return obj;
     }

     void setObj(Obj obj) {
         this.obj = obj;
     }

     @Override
     public Prototype mClone() {
         // TODO Auto-generated method stub
         Prototype prototype = null;
         //调用新的构造方法
         prototype = new ConcretePrototype(getObj());
         prototype.setId(getId());
         return prototype;
     }

 }

 package cn.happy.design_pattern._06prototype.deepclone;

 public class Obj implements Cloneable{
 　　//省略属性，这里也许需要更深层克隆。
     public Object mClone(){
         Obj obj = null;
         try {
             obj = (Obj)this.clone();
         } catch (CloneNotSupportedException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         return obj;
     }
 }

测试类：

 package cn.happy.design_pattern._06prototype.deepclone;

 public class Mmain {

     public static void main(String[] args) {
         ConcretePrototype c1 = new ConcretePrototype();
         ConcretePrototype c2 = (ConcretePrototype)c1.mClone();
         /*
          *  深克隆：c1与c2中Obj的地址不同了
          *  输出：...ConcretePrototype@15db9742,null,...Obj@6d06d69c
          *       ...ConcretePrototype@7852e922,null,...Obj@4e25154f
          */
         System.out.println(c1+","+c1.getId()+","+c1.getObj());
         System.out.println(c2+","+c2.getId()+","+c2.getObj());

     }

 }