MySQL触发器里的流程控制语句 case when .. then else ... end；组合+继承；高级数据库复习

package com.thjava.chap8;
class Cat{
    Cat(){
        System.out.println("Cat eat fish");
    }
}
class IPeople{
    IPeople(){
        System.out.println("People is running");
    }
}
class IStaff extends IPeople{
    IStaff(){
        System.out.println("Staff is working");
    }
}
class IEngineer extends IStaff{
    IEngineer(){
        System.out.println("Emgineer is writing code");
    }
}
class JavaEngineer extends IEngineer{
    Cat c = new Cat();
    IPeople p = new IPeople();
    IStaff s = new IStaff();
    IEngineer e = new IEngineer();
    public JavaEngineer(){
        System.out.println("------------");
        System.out.println("JavaEng is writing Java");
    }
    public static void main(String[] args) {
        System.out.println("------------");
        JavaEngineer err = new JavaEngineer();
        System.out.println("------------");
    }
}

------------
People is running
Staff is working
Emgineer is writing code
Cat eat fish
People is running
People is running
Staff is working
People is running
Staff is working
Emgineer is writing code
------------
JavaEng is writing Java
------------