立即學習:https://edu.csdn.net/course/play/28942/403588?utm_source=blogtoedu
開閉原則
對擴展開放,修改關閉
eg:接口中定義三個方法分別獲取課程的三個屬性
public interface ICourse {
Integer getId();
String getName();
Double getPrice();
}
Java課程業務類實現自己的業務
public class JavaCourse implements ICourse {
private Integer id;
private String name;
private Double price;
public JavaCourse(Integer id, String name, Double price) {
this.id = id;
this.name = name;
this.price = price;
}
@Override
public Integer getId() {
return this.id;
}
@Override
public String getName() {
return this.name;
}
@Override
public Double getPrice() {
return this.price;
}
}
需求變更:java課程需要打折,根據開閉原則不更改原有代碼,創建java打折業務類
public class JavaDiscountCourse extends JavaCourse {
public JavaDiscountCourse(Integer id, String name, Double price){
super(id, name, price);
}
public Double getDiscountPrice(){
return super.getPrice() * 0.8;
}
}
Tips:
這使iCourse獲取不到getDiscountPrice方法
ICourse iCourse = new JavaDiscountCourse(1,"Java虛擬機",1180D);
需要
iCourse = (JavaDiscountCourse)iCourse