设计原则之依赖倒置原则

tip: 需要《设计模式之禅》的书籍，可以联系我

作为程序员一定学习编程之道，一定要对代码的编写有追求，不能实现就完事了。我们应该让自己写的代码更加优雅，即使这会费时费力。

相关规则：

推荐：体系化学习Java（Java面试专题）

1.6大设计规则-迪米特法则
2.6大设计原则-里氏替换原则
3.6大设计规则-开闭原则
4.6大设计规则-单一职责原则
5.6大设计规则-接口隔离原则

依赖倒置原则

依赖倒置原则 Dependence Inversion Principle, DIP。
《设计模式之禅》第三章介绍到：
High level modules should not depend upon low level modules. Both should depend uporabstractions. Abstractions should not depend upon details, Details should depend uponabstractions.

这上面主要讲三个含义，这个是可以在面试中陈述的，说明依赖倒置原则的特点：
1、高层模块不应该依赖低层模块，两者都应该依赖其抽象
2、抽象不能依赖细节
3、细节应该依赖抽象

我们接下来介绍依赖倒置的三种写法

依赖倒置的三种写法

1、接口传递

package com.pany.camp.design.principle.lsp;

/**
 *
 * @description:  车子的抽象类
 * @copyright: @Copyright (c) 2022 
 * @company: Aiocloud
 * @author: panyong 
 * @version: 1.0.0 
 * @createTime: 2023-05-31 13:26
 */
public abstract class Car {

    /**
     * 启动
     *
     * @since 1.0.0
     * @param
     * @return: void
     * @author: panyong
     * @version: 1.0.0
     * @createTime: 2023-05-31 13:28
     */
    abstract void firing();

    /**
     * 车子的牌子
     *
     * @since 1.0.0
     * @param
     * @return: String
     * @author: pany
     * @version: 1.0.0
     * @createTime: 2023-05-31 13:36
     */
    abstract String getName();
}

package com.pany.camp.design.principle.lsp;

/**
 *
 * @description: 法拉利
 * @copyright: @Copyright (c) 2022
 * @company: Aiocloud
 * @author: pany
 * @version: 1.0.0
 * @createTime: 2023-05-31 13:40
 */
public class Ferrari extends Car {
    @Override
    void firing() {
        System.out.println("drive ferrari");
    }

    @Override
    String getName() {
        return "ferrari";
    }
}

package com.pany.camp.design.principle.lsp;
/**
 *
 * @description:  保时捷
 * @copyright: @Copyright (c) 2022
 * @company: Aiocloud
 * @author: pany
 * @version: 1.0.0
 * @createTime: 2023-05-31 13:30
 */
public class Porsche extends Car {
    
    @Override
    void firing() {
        System.out.println("drive porsche");
    }

    @Override
    String getName() {
        return "porsche";
    }
}

package com.pany.camp.design.principle.lsp;

public class User {

    public void drive(Car car) {
        car.firing();
        System.out.println("drive " + car.getName());
    }

    public static void main(String[] args) {
        User user = new User();

        // 我可以换成其他的方式，并没有改变代码的逻辑
        user.drive(new Porsche());
        user.drive(new Ferrari());
    }
}

2、构造器传递

package com.pany.camp.design.principle.dip;

/**
 *
 * @description: 电脑
 * @copyright: @Copyright (c) 2022
 * @company: Aiocloud
 * @author: pany
 * @version: 1.0.0
 * @createTime: 2023-05-31 21:13
 */
public interface Computer {

    /**
     * 打游戏
     *
     * @since 1.0.0
     * @param
     * @return: void
     * @author: pany
     * @version: 1.0.0
     * @createTime: 2023-05-31 21:14
     */
    void playGame();
}

package com.pany.camp.design.principle.dip;

/**
 *
 * @description: 惠普
 * @copyright: @Copyright (c) 2022
 * @company: Aiocloud
 * @author: pany
 * @version: 1.0.0
 * @createTime: 2023-05-31 21:15
 */
public class Hp implements Computer {

    @Override
    public void playGame() {
        System.out.println("I use Hp computer, start play game");
    }
}

package com.pany.camp.design.principle.dip;

/**
 *
 * @description:  学生
 * @copyright: @Copyright (c) 2022
 * @company: Aiocloud
 * @author: pany
 * @version: 1.0.0
 * @createTime: 2023-05-31 21:15
 */
public class Student {

    private Computer computer;

    public Student(Computer computer) {
        this.computer = computer;
    }

    /**
     * 开始打游戏
     *
     * @since 1.0.0
     * @param
     * @return: void
     * @author: pany
     * @version: 1.0.0
     * @createTime: 2023-05-31 21:17
     */
    public void startPlayGame() {
        this.computer.playGame();
    }

    /**
     * 测试方法
     *
     * @since 1.0.0
     * @param
     * @param args
     * @return: void
     * @author: pany
     * @version: 1.0.0
     * @createTime: 2023-05-31 21:17
     */
    public static void main(String[] args) {
        Student student = new Student(new Hp());
        student.startPlayGame();
    }
}

3、set 方法传递在这里插入代码片

在构造器例子的基础上，新写一个 User，通过 set 方法传递。

package com.pany.camp.design.principle.dip;

/**
 *
 * @description:  学生
 * @copyright: @Copyright (c) 2022
 * @company: Aiocloud
 * @author: pany
 * @version: 1.0.0
 * @createTime: 2023-05-31 21:15
 */
public class User {

    private Computer computer;

    public void setComputer(Computer computer) {
        this.computer = computer;
    }

    /**
     * 开始打游戏
     *
     * @since 1.0.0
     * @param
     * @return: void
     * @author: pany
     * @version: 1.0.0
     * @createTime: 2023-05-31 21:17
     */
    public void startPlayGame() {
        this.computer.playGame();
    }

    /**
     * 测试方法
     *
     * @since 1.0.0
     * @param
     * @param args
     * @return: void
     * @author: pany
     * @version: 1.0.0
     * @createTime: 2023-05-31 21:17
     */
    public static void main(String[] args) {
        User user = new User();
        user.setComputer(new Hp());
        user.startPlayGame();
    }
}