五、面向对象之继承

//Person p = new Student();  // Person父类  Student子类
//System.out.println(p instanceof Person); // instanceof判断p对象是否能使用父类方法
// 继承是is关系，组合是has关系。
public class Object1 {
    public static void main(String[] args) {
        //Person p = new Person("小王",24);
        //Student s = new Student("莉莉",21,100);
        PrimaryStudent m = new PrimaryStudent("莉莉",21,100,5);
        //System.out.println(p.getAge());
        //System.out.println(s.getAge());
        System.out.println(m.getScore());
    }
}
class Person{
    protected String name;  // protected允许子类访问父类的字段和方法
    protected int age;
    public Person(String name,int age){
        this.name = name;
        this.age = age;
    }
    public String getName(){
        return name;
    }
    public int getAge(){
        return age;
    }
}
class Student extends Person{
    protected int score;
    public Student(String name,int age,int score){
        super(name,age);   // 调用父类的构造方法Person(String name,int age)
        this.score = score;
    }
    public int getScore(){
        return score;
    }
}
class PrimaryStudent extends Student{
    protected int grade;
    public PrimaryStudent(String name,int age,int score,int grade){
        super(name,age,score);
        this.grade = grade;
    }
    public int getGrade(){
        return grade;
    }
}