设计模式 六、原型模式

原型模式：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。

原型模式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。

浅复制，深复制

浅复制，复制值类型的实域，对引用类型的实域只复制引用不复制引用的对象，即克隆出来的对象b和原对象a引用同一个对象类型的实域c，在 b的方法 改变 b中的c 会影响 a中的c。

//简历类，实现Cloneable接口
public class Resume implements Cloneable {
    private String name;
    private String sex;
    private String age;
    private String time;
    private String company;

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

    public void SetInfo(String sex, String age) {
        this.sex = sex;
        this.age = age;
    }

    public void SetWork(String time, String company) {
        this.time = time;
        this.company = company;
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Object object = super.clone();
        return object;
    }

    @Override
    public String toString() {
        return "Resume{" +
                "name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", age='" + age + '\'' +
                ", time='" + time + '\'' +
                ", company='" + company + '\'' +
                '}';
    }

    public static void main(String[] args) throws CloneNotSupportedException {
        Resume resume1 = new Resume("RagdoLL");
        resume1.SetInfo("man", "21");
        resume1.SetWork("2022", "Ubisoft");

        Resume resume2 = (Resume) resume1.clone();

        System.out.println(resume1.toString());
        System.out.println(resume2.toString());
    }
}

输出：

Resume{name='RagdoLL', sex='man', age='21', time='2022', company='Ubisoft'}
Resume{name='RagdoLL', sex='man', age='21', time='2022', company='Ubisoft'}

如果改为对象 Work 持有time 和 company实域，浅复制无法完成引用对象的复制，只复制了引用

//简历类，实现Cloneable接口
public class Resume implements Cloneable {
    private String name;
    private String sex;
    private String age;

    private Work work;

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

    public void SetInfo(String sex, String age) {
        this.sex = sex;
        this.age = age;
    }

    public void SetWork(String time, String company) {
        this.work.setTime(time);
        this.work.setCompany(company);
    }

    @Override
    protected Object clone() throws CloneNotSupportedException {
        Object object = super.clone();
        return object;
    }

    @Override
    public String toString() {
        return "Resume{" +
                "name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", age='" + age + '\'' +
                ", time='" + work.getTime() + '\'' +
                ", company='" + work.getCompany() + '\'' +
                '}';
    }

    public static void main(String[] args) throws CloneNotSupportedException {
        Resume resume1 = new Resume("RagdoLL");
        resume1.SetInfo("man", "21");
        resume1.SetWork("2022", "Ubisoft");

        Resume resume2 = (Resume) resume1.clone();
        resume2.SetWork("2021","Action");

        System.out.println(resume1.toString());
        System.out.println(resume2.toString()); //改变resume2的Work，resume1的Work对象的值被覆盖
    }
}

深复制，对引用对象Work也进行复制。

//简历类，实现Cloneable接口
public class Resume implements Cloneable {
    private String name;
    private String sex;
    private String age;

    private Work work;

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

    //克隆引用对象的接口
    public void setWork(Work work) {
        this.work = work;
    }

    public void SetInfo(String sex, String age) {
        this.sex = sex;
        this.age = age;
    }

    public void SetWork(String time, String company) {
        this.work.setTime(time);
        this.work.setCompany(company);
    }

    @Override
    protected Resume clone() throws CloneNotSupportedException {
        //这一步还是浅克隆
        Resume resume = (Resume) super.clone();
        //完成深克隆
        resume.setWork((Work) work.clone());
        return resume;
    }

    @Override
    public String toString() {
        return "Resume{" +
                "name='" + name + '\'' +
                ", sex='" + sex + '\'' +
                ", age='" + age + '\'' +
                ", time='" + work.getTime() + '\'' +
                ", company='" + work.getCompany() + '\'' +
                '}';
    }

    public static void main(String[] args) throws CloneNotSupportedException {
        Resume resume1 = new Resume("RagdoLL");
        resume1.SetInfo("man", "21");
        resume1.SetWork("2022", "Ubisoft");

        Resume resume2 = resume1.clone();
        resume2.SetWork("2021", "Action");

        System.out.println(resume1.toString());
        System.out.println(resume2.toString());
    }
}

输出：

Resume{name='RagdoLL', sex='man', age='21', time='2022', company='Ubisoft'}
Resume{name='RagdoLL', sex='man', age='21', time='2021', company='Action'}