大话设计模式之原型模式总结-java实现

最新推荐文章于 2021-06-18 22:43:45 发布

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最新推荐文章于 2021-06-18 22:43:45 发布

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分类专栏：设计模式文章标签： java 设计模式

本文链接：https://blog.youkuaiyun.com/qq_26814945/article/details/82343817

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本文介绍原型模式的实现方式及深浅复制的区别，通过简历类的实例展示如何利用原型模式快速创建对象，并深入探讨了深复制与浅复制在对象复制过程中的不同表现。

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注：示例来自《大话设计模式》

现有需求如下要求有一个简历类必须要有姓名可以设置性别和年龄可以设置工作经历最终我需要写三份简历代码初步实现如下

简历类

package Test09;

//简历
public class Resume {

    private String name;
    private String sex;
    private String age;
    private String timeArea;
    private String company;

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

    //设置个人信息
    public void SetPersonalInfo(String sex, String age)
    {
        this.sex = sex;
        this.age = age;
    }

    //设置工作经历
    public void SetWorkExperience(String timeArea, String company)
    {
        this.timeArea = timeArea;
        this.company = company;
    }

    //显示
    public void Display()
    {
        System.out.println(name+" "+sex+" "+age);
        System.out.println(timeArea+" "+company);
    }

}

客户端代码

package Test09;

public class Program {

    public static void main(String[] args) {

        Resume a = new Resume("大鸟");
        a.SetPersonalInfo("男", "29");
        a.SetWorkExperience("1998-2000", "XX公司");

        Resume b = new Resume("大鸟");
        b.SetPersonalInfo("男", "29");
        b.SetWorkExperience("1998-2000", "XX公司");

        Resume c = new Resume("大鸟");
        c.SetPersonalInfo("男", "29");
        c.SetWorkExperience("1998-2000", "XX公司");

        a.Display();
        b.Display();
        c.Display();

    }

}

上面的代码三份简历需要三次实例化很麻烦我们看看下面的写法

客户端代码

package Test09;

public class Program {

    public static void main(String[] args) {

        Resume a = new Resume("大鸟");
        a.SetPersonalInfo("男", "29");
        a.SetWorkExperience("1998-2000", "XX公司");

        Resume b = a;

        Resume c = a;

        a.Display();
        b.Display();
        c.Display();

    }

}

上面的代码其实是传引用而不是传值这样做就如同是在b纸张和c纸张上写着简历在a处一样没有实际的内容

接下来采用原型模式(Clone克隆)进行重构代码如下

简历类

package Test09;

//简历
public class Resume implements Cloneable {

    private String name;
    private String sex;
    private String age;
    private String timeArea;
    private String company;

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

    //设置个人信息
    public void SetPersonalInfo(String sex, String age)
    {
        this.sex = sex;
        this.age = age;
    }

    //设置工作经历
    public void SetWorkExperience(String timeArea, String company)
    {
        this.timeArea = timeArea;
        this.company = company;
    }

    //显示
    public void Display()
    {
        System.out.println(name+" "+sex+" "+age);
        System.out.println(timeArea+" "+company);
    }

    public Object Clone() throws CloneNotSupportedException
    {
        return (Object)super.clone();
    }

}

客户端代码

package Test09;

public class Program {

    public static void main(String[] args) throws CloneNotSupportedException {

        Resume a = new Resume("大鸟");
        a.SetPersonalInfo("男", "29");
        a.SetWorkExperience("1998-2000", "XX公司");

        Resume b = (Resume)a.Clone();
        b.SetWorkExperience("1998-2006", "YY企业");

        Resume c = (Resume)a.Clone();
        c.SetPersonalInfo("男", "24");

        a.Display();
        b.Display();
        c.Display();

    }

}

clone()方法是这样如果字段是值类型的则对该字段执行逐位复制如果字段是引用类型则复制引用但不复制引用的对象因此原始对象及其复本引用同一对象就是说如果简历类中有对象引用那么引用的对象数据是不会被克隆过来的
例如我们单独写个工作经历类里面有时间区间和公司名称属性代码如下

工作经历类

package Test09;

//工作经历
public class WorkExperience {

    private String workDate;
    private String company;

    public String getWorkDate() {
        return workDate;
    }
    public void setWorkDate(String workDate) {
        this.workDate = workDate;
    }
    public String getCompany() {
        return company;
    }
    public void setCompany(String company) {
        this.company = company;
    }

}

简历类

package Test09;

//简历
public class Resume implements Cloneable {

    private String name;
    private String sex;
    private String age;

    private WorkExperience work;

    public Resume(String name)
    {
        this.name = name;
        work = new WorkExperience();
    }

    //设置个人信息
    public void SetPersonalInfo(String sex, String age)
    {
        this.sex = sex;
        this.age = age;
    }

    //设置工作经历
    public void SetWorkExperience(String workDate, String company)
    {
        work.setWorkDate(workDate);
        work.setCompany(company);
    }

    //显示
    public void Display()
    {
        System.out.println(name+" "+sex+" "+age);
        System.out.println(work.getWorkDate()+" "+work.getCompany());
    }

    public Object Clone() throws CloneNotSupportedException
    {
        return (Object)super.clone();
    }

}

客户端代码

package Test09;

public class Program {

    public static void main(String[] args) throws CloneNotSupportedException {

        Resume a = new Resume("大鸟");
        a.SetPersonalInfo("男", "29");
        a.SetWorkExperience("1998-2000", "XX公司");

        Resume b = (Resume)a.Clone();
        b.SetWorkExperience("1998-2006", "YY企业");

        Resume c = (Resume)a.Clone();
        c.SetPersonalInfo("男", "24");
        c.SetWorkExperience("1998-2003", "ZZ企业");

        a.Display();
        b.Display();
        c.Display();

    }

}

可以看到我给a b c三个引用设置工作经历三个引用都指向了同一个对象这叫做潜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

但我们可能更需要这样的一种需求把要复制的对象所引用的对象都复制一遍比如刚才的例子我们希望是a b c三个引用的对象都是不同的即深复制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被引用的对象下面是深复制实现的代码

工作经历类

package Test09;

//工作经历
public class WorkExperience implements Cloneable {

    private String workDate;
    private String company;

    public String getWorkDate() {
        return workDate;
    }
    public void setWorkDate(String workDate) {
        this.workDate = workDate;
    }
    public String getCompany() {
        return company;
    }
    public void setCompany(String company) {
        this.company = company;
    }

    public Object Clone() throws CloneNotSupportedException
    {
        return (Object)super.clone();
    }

}

简历类

package Test09;

//简历
public class Resume implements Cloneable {

    private String name;
    private String sex;
    private String age;

    private WorkExperience work;

    public Resume(String name)
    {
        this.name = name;
        work = new WorkExperience();
    }

    private Resume(WorkExperience work) throws CloneNotSupportedException
    {
        this.work = (WorkExperience)work.Clone();
    }

    //设置个人信息
    public void SetPersonalInfo(String sex, String age)
    {
        this.sex = sex;
        this.age = age;
    }

    //设置工作经历
    public void SetWorkExperience(String workDate, String company)
    {
        work.setWorkDate(workDate);
        work.setCompany(company);
    }

    //显示
    public void Display()
    {
        System.out.println(name+" "+sex+" "+age);
        System.out.println(work.getWorkDate()+" "+work.getCompany());
    }

    public Object Clone() throws CloneNotSupportedException
    {
        Resume obj = new Resume(this.work);

        obj.name = this.name;
        obj.sex = this.sex;
        obj.age = this.age;

        return obj;
    }

}

客户端代码

package Test09;

public class Program {

    public static void main(String[] args) throws CloneNotSupportedException {

        Resume a = new Resume("大鸟");
        a.SetPersonalInfo("男", "29");
        a.SetWorkExperience("1998-2000", "XX公司");

        Resume b = (Resume)a.Clone();
        b.SetWorkExperience("1998-2006", "YY企业");

        Resume c = (Resume)a.Clone();
        c.SetPersonalInfo("男", "24");
        c.SetWorkExperience("1998-2003", "ZZ企业");

        a.Display();
        b.Display();
        c.Display();

    }

}