因为你的超级人没有'在你的子类（ Student 和 Staff ）中有一个默认构造函数，你必须调用超类构造函数第一个语句。

Since your super class Person doesn't have a default constructor, in your sub classes (Student and Staff), you must call the super class constructor as the first statement.

你应该像这样定义你的子类构造函数：

You should define your sub class constructors like this:

Student() {
    super("a_string_value", an_int_value);// You have to pass String and int values to super class
}

Staff() {
    super("a_string_value", an_int_value); // You have to pass String and int values to super class
}