Opening and closing principle Open Closed Principle

Introduce the principle of open and closed:

1) closing principle (Open Closed Principle) programming the most basic and important design principles
2) a software entity, such as classes, modules and functions should be open for extension (for provider), closed for modification (to the consumer) . Abstract framework for building, implemented with extension detail.
3) When the software needs to change, try to achieve changes in behavior by extending the software entity, rather than to achieve change by modifying existing code.
4) follow other programming principles and design patterns object is to follow the principle of opening and closing.

---

 

  

Examples of errors

Package com.kittenplus.principle.ocp; 

    public  class OCP {
         public  static  void main (String [] args) { 
            GraphicEditor GE = new new GraphicEditor (); 
            ge.drawShape ( new new the Rectangle ()); 
            ge.drawCircle ( new new Circle () ); 
        }} 
        
    // this is a drawing for class 
        class GraphicEditor {
     // receiving Shape object, and then draw a different pattern according to the type 
        public  void the drawShape (Shape S) {
         IF (s.m_type ==. 1 ) 
        drawRectangle (S ); 
        the else  IF (s.m_type == 2)
        drawCircle(s);
        }
        public void drawRectangle(Shape r) {
        System.out.println("绘制矩形");}
        public void drawCircle(Shape r) {
        System.out.println("绘制圆形");
        }}
    //Shape 类 基类
        class Shape {
        int m_type;
        }
        class Rectangle extends Shape {
        Rectangle() {
        super.m_type = 1;
        }}
        class Circle extends Shape {
        Circle() {
        super.m_type = 2;
        }
}

 

 

 

Package com.kittenplus.principle.ocp; 

    public  class OCP {
         public  static  void main (String [] args) { 
            GraphicEditor GE = new new GraphicEditor (); 
            ge.drawShape ( new new the Rectangle ()); 
            ge.drawShape ( new new Circle () ); 
            ge.drawShape ( new new Triangle ()); 
            ge.drawShape ( new new OtherGraphic ()); 
        }} 
        
    // this is a drawing for class 
        class GraphicEditor {
     // receiving Shape object, and then draw a different pattern according to type 
        public  void drawShape(Shape s) {
            s.draw();
        }

    }
    //Shape 类 基类
        abstract class Shape {
        int m_type;
        public abstract void draw();//抽象方法
        }
        
        class Rectangle extends Shape {
        Rectangle() {
        super.m_type = 1;
        }
        @Override
        public void draw() {
        System.out.println(" 绘制矩形");    
        }
    }
        class Circle extends Shape {
        Circle() {
        super.m_type = 2;
        }
        @Override
        public void draw() {
        System.out.println(" 绘制圆形");
        }
    }
        class Triangle extends Shape{
            Triangle(){
                super.m_type=3;
            }
            @Override
            public void draw() {
            System.out.println(" 绘制三角形");    
            }
    }
        class OtherGraphic extends{The Shape 
            OtherGraphic () { 
                Super .m_type. 4 = ; 
            } 
            @Override 
            public  void Draw () { 
            System.out.println ( "drawing other graphic" );     
            } 
    }