关于java:Java中的原型模式

原型模式简介

• 模式属于创立型模式，它提供了一种创建对象的最佳形式。
• 用于创立反复的对象，同时又能保障性能。
• 这种模式是实现了一个原型接口，该接口用于创立以后对象的克隆。当间接创建对象的代价比拟大时，则采纳这种模式。
• 例如，一个对象须要在一个高代价的数据库操作之后被创立。咱们能够缓存该对象，在下一个申请时返回它的克隆，在须要的时候更新数据库，以此来缩小数据库调用。

浅克隆

类 Book 实现 Cloneable 接口并重写 clone 办法

public class Book implements Cloneable {
    private String name;// 书名
    private Date publishDate;// 公布日期

    public Book() {}

    public Book(String name, Date publishDate) {
        this.name = name;
        this.publishDate = publishDate;
    }

    public String getName() {return name;}

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

    public Date getPublishDate() {return publishDate;}

    public void setPublishDate(Date publishDate) {this.publishDate = publishDate;}

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

    @Override
    public String toString() {
        return "Book{" +
                "name='" + name + '\'' +
                ", publishDate=" + publishDate +
                '}';
    }
}

测试类

public class Test {public static void main(String[] args) throws CloneNotSupportedException {
        String name = "Java 设计模式";
        Date publishDate = new Date();

        Book book = new Book(name, publishDate);
        // 克隆出对象
        Book clone = (Book) book.clone();

        System.out.println(book);
        System.out.println(book.hashCode());
        System.out.println(clone);
        System.out.println(clone.hashCode());

        System.out.println("==================");

        publishDate.setTime(publishDate.getTime() + 2000);// 批改工夫
        System.out.println(book);
        System.out.println(book.hashCode());
        System.out.println(clone);
        System.out.println(clone.hashCode());

        /**
         * 测试后果：批改了工夫，源对象和克隆的对象的工夫，都产生了扭转
         * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:33 CST 2021}
         * 2093631819
         * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:33 CST 2021}
         * 2074407503
         * ==================
         * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:35 CST 2021}
         * 2093631819
         * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:35 CST 2021}
         * 2074407503
         */
    }
}

测试后果

Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:33 CST 2021}
2093631819
Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:33 CST 2021}
2074407503
==================
Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:35 CST 2021}
2093631819
Book{name='Java 设计模式', publishDate=Wed Dec 29 12:17:35 CST 2021}
2074407503

深克隆

类 Book 实现 Cloneable 接口并重写 clone 办法

public class Book implements Cloneable {
    private String name;// 书名
    private Date publishDate;// 公布日期

    public Book() {}

    public Book(String name, Date publishDate) {
        this.name = name;
        this.publishDate = publishDate;
    }

    public String getName() {return name;}

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

    public Date getPublishDate() {return publishDate;}

    public void setPublishDate(Date publishDate) {this.publishDate = publishDate;}

    @Override
    protected Object clone() throws CloneNotSupportedException {Object obj = super.clone();
        Book book = (Book) obj;

        // 将源对象的属性也进行克隆，即深克隆
        book.publishDate = (Date) book.publishDate.clone();
        return obj;
    }

    @Override
    public String toString() {
        return "Book{" +
                "name='" + name + '\'' +
                ", publishDate=" + publishDate +
                '}';
    }
}

测试类

public class Test {public static void main(String[] args) throws CloneNotSupportedException {
        String name = "Java 设计模式";
        Date publishDate = new Date();

        Book book = new Book(name, publishDate);
        // 克隆出对象
        Book clone = (Book) book.clone();

        System.out.println(book);
        System.out.println(book.hashCode());
        System.out.println(clone);
        System.out.println(clone.hashCode());

        System.out.println("==================");

        publishDate.setTime(publishDate.getTime() + 2000);
        System.out.println(book);
        System.out.println(book.hashCode());
        System.out.println(clone);
        System.out.println(clone.hashCode());

        /**
         * 测试后果：批改了工夫，源对象的工夫，产生了扭转，但克隆的对象的工夫没有扭转
         * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:47 CST 2021}
         * 2093631819
         * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:47 CST 2021}
         * 2074407503
         * ==================
         * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:49 CST 2021}
         * 2093631819
         * Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:47 CST 2021}
         * 2074407503
         */
    }
}

测试后果

Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:47 CST 2021}
2093631819
Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:47 CST 2021}
2074407503
==================
Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:49 CST 2021}
2093631819
Book{name='Java 设计模式', publishDate=Wed Dec 29 12:41:47 CST 2021}
2074407503