java 用继承完成①学校有2种员工：助教（Assistant）、收银员（Cashier）。助教的行为action()是：协助老师修改作业；收银员的行为action()是:在餐馆打工收银。②员工可以

以下是Java代码实现：

```
//员工类
public class Employee {
public void action() {
//员工的行为
}
}

//助教类，继承自员工类
public class Assistant extends Employee {
@Override
public void action() {
System.out.println("正在协助老师批作业...");
}
}

//收银员类，继承自员工类
public class Cashier extends Employee {
@Override
public void action() {
System.out.println("正在餐馆打工收银...");
}
}

//学校类
public class School {
public void enter(Employee employee) {
//员工进入学校
}

public void run() {
//学校运营
}
}

//测试类
public class Test {
public static void main(String[] args) {
School school = new School();
Assistant xiaodong = new Assistant();
Cashier xiaoming = new Cashier();
school.enter(xiaodong);
xiaodong.action();
school.enter(xiaoming);
xiaoming.action();
}
}
```

输出结果为：

```
正在协助老师批作业...
正在餐馆打工收银...
```