设计模式七大原则五之开闭原则

基本介绍

1）开闭原则Open Closed Principle，重要设计原则

2）一个软件实体如类，模块和函数应该对扩展开放，对修改关闭。用抽象构建框架，用实现扩展细节

3）当软件需要变化时，尽量通过扩展软件实体的行为来实现变化，而不是通过修改已有的代码来实现变化

4）编程中遵循其他原则，以及使用设计模式的目的就是遵循开闭原则

package com.hy.principle.ocp;

/**
 * @author hanyong
 * @date 2020/9/23 0:19
 */
public class Ocp {


    public static void main(String[] args) {
        GraphicEditor graphicEditor = new GraphicEditor();
        graphicEditor.drawShap(new Rectangle());
        graphicEditor.drawShap(new Circle());
        graphicEditor.drawShap(new Triangle());

    }


}


class GraphicEditor {

    public void drawShap(Shape shape) {
        if (shape.m_type == 1) {
            drawRectangle();
        } else if (shape.m_type == 2) {
            drawCircle();
        }else if(shape.m_type==3){
            drawTriangle();
        }
    }

    public void drawRectangle() {
        System.out.println("绘制矩形");
    }

    public void drawCircle() {
        System.out.println("绘制圆形");
    }

    public void drawTriangle() {
        System.out.println("绘制三角形");
    }
}

class Shape {
    int m_type;
}

class Rectangle extends Shape {
    Rectangle() {
        super.m_type = 1;
    }
}

class Circle extends Shape {
    Circle() {
        super.m_type = 2;
    }
}

//添加一种,改动量太大，调用方也会发生变化
class Triangle extends Shape {
    Triangle() {
        super.m_type = 3;
    }
}

package com.hy.principle.ocp.improve;

/**
 * @author hanyong
 * @date 2020/9/23 0:19
 */
public class Ocp {


    public static void main(String[] args) {
        GraphicEditor graphicEditor = new GraphicEditor();
        graphicEditor.drawShap(new Rectangle());
        graphicEditor.drawShap(new Circle());
        graphicEditor.drawShap(new Triangle());
        graphicEditor.drawShap(new WujiaoStar());
    }


}


class GraphicEditor {

    public void drawShap(Shape shape) {
        shape.draw();
    }


}

abstract class Shape {
    int m_type;
//使用方没有变动，修改关闭
    abstract void draw();

}

class Rectangle extends Shape {
    Rectangle() {
        super.m_type = 1;
    }

    @Override
    void draw() {
        System.out.println("绘制矩形");
    }
}

class Circle extends Shape {
    Circle() {
        super.m_type = 2;
    }

    @Override
    void draw() {
        System.out.println("绘制圆形");
    }
}

class Triangle extends Shape {
    Triangle() {
        super.m_type = 3;
    }

    @Override
    void draw() {
        System.out.println("绘制三角形");
    }

}
//扩展开放
//添加一种,改动少
class WujiaoStar extends Shape {

    @Override
    void draw() {
        System.out.println("绘制五角星");
    }
}

设计模式七大原则五之开闭原则

原文：https://www.cnblogs.com/yongzhewuwei/p/13715743.html