（1）写一个基类Employee，有一个非静态方法void computePay()和一个静态方法expenseAllowance()。computePay只需要打印字符串表示自己是Employee类的computePay方法即可；expenseAllowance只需要打印字符串表示自己是Employee类的expenseAllowance方法即可。 （2）写一个类Manager派生自Employee，覆盖了父类的computePay()和expenseAllowance()方法。computePay只需要打印字符串表示自己是Manager类的computePay方法即可；expenseAllowance只需要打印字符串表示自己是Manager类的expenseAllowance方法即可。 写一个类TestEmp，在main函数中声明一个Employee的对象emp，一个Manager类型的对象man。并将man向上塑性为Employee类型的引用变量emp2。分别调用emp. computePay(), man. computePay(), emp2. computePay()以及emp. expenseAllowance (), man. expenseAllowance (), emp2. expenseAllowance()。

代码如下：

class Employee {
    public void computePay() {
        System.out.println("This is Employee's computePay method");
    }

    public static void expenseAllowance() {
        System.out.println("This is Employee's expenseAllowance method");
    }
}

class Manager extends Employee {
    @Override
    public void computePay() {
        System.out.println("This is Manager's computePay method");
    }

    @Override
    public static void expenseAllowance() {
        System.out.println("This is Manager's expenseAllowance method");
    }
}

public class TestEmp {
    public static void main(String[] args) {
        Employee emp = new Employee();
        Manager man = new Manager();
        Employee emp2 = man;

        emp.computePay();
        man.computePay();
        emp2.computePay();

        emp.expenseAllowance();
        man.expenseAllowance();
        emp2.expenseAllowance();
    }
}

输出结果为：

This is Employee's computePay method
This is Manager's computePay method
This is Manager's computePay method
This is Employee's expenseAllowance method
This is Manager's expenseAllowance method
This is Employee's expenseAllowance method

可以看到，调用同名方法时，子类方法会覆盖父类方法，但静态方法不会发生重写，只会隐藏父类方法。使用向上转型后，被引用的变量只能调用其类型或其父类中定义的方法。