继承格式： 

package javatest2;

public class people {
     int age;
    double workday;


    public people(int age, double workday) {
        this.age = age;
        this.workday = workday;
    }
}

package javatest2;

public class student extends people {
     int studyday;

    public student(int age, double workday, int studyday) {
        super(age, workday);
        this.studyday = studyday;
    }




}

package javatest2;

public class test {
    public static void main(String[] args) {


    student s =new student(5,5,5);
    System.out.println(s.studyday);
    }
}