原型模式

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原型模式

olv123 2018-12-26 20:11:24 浏览788
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在介绍原型模式前,首先先了解下Java中的clone()方法。object中自带的本地方法

protected native Object clone() throws CloneNotSupportedException;

但是该方法不可以直接使用,需要两步操作
①实现Cloneable接口,这是一个标记接口,自身没有方法。
② 重写clone()方法
举一个小例子,看下clone()的使用方法:
编写一个Teacher类,属性name和age,Teacher类实现cloneable接口,并重写clone()方法

public class Teacher implements Cloneable {
    String name;
    Integer age;

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Teacher{" +
                "name='" + name + '\'' +
                ", age='" + age + '\'' +
                '}';
    }
    @Override
    protected Object clone() throws CloneNotSupportedException {
        return super.clone();
    }
}

编写一个学生Stu类,属性name、age、Teacher,给每个学生指定一个老师,Stu类实现cloneable接口,并重写clone()方法

public class Stu implements Cloneable {
    String name;
    Integer age;
    Teacher teacher;

    public Stu() {
        System.out.println("测试clone方法是否调用构造方法");
    }

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Teacher getTeacher() {
        return teacher;
    }

    public void setTeacher(Teacher teacher) {
        this.teacher = teacher;
    }

    @Override
    public String toString() {
        return "Stu{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", teacher=" + teacher +
                '}';
    }
    @Override
    protected Object clone() throws CloneNotSupportedException {
       return super.clone();
    }
}

编写一个测试类:

public static void main(String [] args){
        Teacher t1 = new Teacher();
        t1.setAge(32);
        t1.setName("wang Teacher");
        Stu s1 = new Stu();
        s1.setName("xiao ming");
        s1.setAge(22);
        s1.setTeacher(t1);
        System.out.println("复制前的学生1:"+s1);
        try {
            Stu s2 = (Stu) s1.clone();
            s2.setName("da ming");
            s2.setAge(24);
            Teacher t2 = s2.getTeacher();
            t2.setName("zhao Teacher");
            t2.setAge(34);
            s2.setTeacher(t2);
            System.out.println("复制后的学生1:"+s1);
            System.out.println("复制后的学生2:"+s2);
            System.out.println("teacher的地址"+s1.getTeacher().hashCode());
            System.out.println("teacher的地址"+s2.getTeacher().hashCode());

        } catch (CloneNotSupportedException e) {
        }

    }

实验结果:

Connected to the target VM, address: '127.0.0.1:52313', transport: 'socket'
测试clone方法是否调用构造方法
复制前的学生1:Stu{name='xiao ming', age=22, teacher=Teacher{name='wang Teacher', age='32'}}
复制后的学生1:Stu{name='xiao ming', age=22, teacher=Teacher{name='zhao Teacher', age='34'}}
复制后的学生2:Stu{name='da ming', age=24, teacher=Teacher{name='zhao Teacher', age='34'}}
teacher的地址1763847188
teacher的地址1763847188
Disconnected from the target VM, address: '127.0.0.1:52313', transport: 'socket'

Process finished with exit code 0

显然,在给学生da ming指定老师名字和年龄时,把xiao ming学生的老师也修改了,这就是clone()方法的浅拷贝造成的。复制xiao ming学生的name和age时,成功复制了对应的存储空间到daming中,其实,teacher的存储空间已对应的复制了,只是复制的是相同的引用,看结果中的两个老师的地址都是1763847188,这两个地址指的是同一存储空间,所以,在修改一个老师的同时也就把另一名老师修改了。解决办法就是深拷贝,重写学生类中的clone()方法,

/**
     * 调用clone()方法时,student中的name和age复制了空间,teacher也复制了空间,但空间中存的引用值是不会变的,还指向的是原来的引用
     */
    @Override
    protected Object clone() throws CloneNotSupportedException {
        Stu newstudent = (Stu) super.clone();
        newstudent.teacher = (Teacher) teacher.clone();
        return newstudent;
    }

实验结果:

测试clone方法是否调用构造方法
复制前的学生1:Student{name='xiao ming', age='22', teacher=Teacher{name='wang Teacher', age='32'}}
复制后的学生1:Student{name='xiao ming', age='22', teacher=Teacher{name='wang Teacher', age='32'}}
复制后的学生2:Student{name='da ming', age='24', teacher=Teacher{name='zhao Teacher', age='34'}}
teacher的地址1836019240
teacher的地址325040804

Process finished with exit code 0

完成~
=========================分割线==================
原型模式为设计模式其中之一,也是重新实现的clone()方法
原型模式可以通过一个对象实例确定创建对象的种类,并且通过拷贝创建新的对象。原型模式实际上就是从一个对象创建另一个新的对象,使新的对象有具有原对象的特征。
编写一个个人individual类和工作经历work类,并直接复制成一个新的对象:
work类:

public class Work {
    String address;
    String company;
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    public String getCompany() {
        return company;
    }
    public void setCompany(String company) {
        this.company = company;
    }
    @Override
    public String toString() {
        return "work{" +
                "address='" + address + '\'' +
                ", company='" + company + '\'' +
                '}';
    }
}

individual类

public class Individual implements Cloneable{
    String name;
    Integer age;
    Work work;

    public Individual() {
        work = new Work();
    }

    public String getName() {
        return name;
    }

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

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

/*    public Work getWork() {
        return work;
    }

    public void setWork(Work work) {
        this.work = work;
    }*/

     public void setWork(String address,String company) {
        work.address = address;
        work.company = company;
    }

    public void setperson(String name,Integer age){
        this.age = age;
        this.name = name;
    }

    @Override
    public String toString() {
        return "Individual{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", work=" + work +
                '}';
    }

    @Override
    protected Individual clone() throws CloneNotSupportedException {

        Individual individual = new Individual();
        individual.setperson(this.name,this.age);
        individual.setWork(this.work.address,this.work.company);
        return individual;
    }

}

测试类


public class PrototypeDemo {

    /**
     * 实现原型模式 实质就是实现clone()方法的深拷贝
     * 1.实现cloneable()接口,并重写object的clone()方法
     * 2. 在clone()方法中实现拷贝,并返回一个拷贝实体。
     */
    public static void main(String [] args) throws CloneNotSupportedException {
        Individual individual1 = new Individual();
        individual1.setperson("xiaoming",22);
        individual1.setWork("beijing","baidu");
        System.out.println("个人信息拷贝前individual1"+individual1);

        Individual individual2 = individual1.clone();
        individual2.setperson("daming",24);
        individual2.setWork("hangzhou","ali");
        System.out.println("个人信息拷贝后individual1"+individual1);
        System.out.println("个人信息拷贝后individual2"+individual2);
    }
}```  
实验结果

个人信息拷贝前individual1Individual{name='xiaoming', age=22, work=work{address='beijing', company='baidu'}}
个人信息拷贝后individual1Individual{name='xiaoming', age=22, work=work{address='beijing', company='baidu'}}
个人信息拷贝后individual2Individual{name='daming', age=24, work=work{address='hangzhou', company='ali'}}

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