CoreJava/exp3/ExtendsDemo.java

package exp3;


//类-人
class Person{
    //成员变量
    String name;    //姓名
    int age;    //年龄

    //无参构造"人"
    public Person(){
        this.name = "无名";
        this.age = 18;
    }

    //有参构造"人"
    public Person(String name, int age){
        this.name = name;
        this.age = age;
    }


    //设置姓名
    void setName(String name){
        this.name = name;
    }

    //设置年龄
    void setAge(int age){
        this.age = age;
    }

    //行为-吃饭
    void eat(Person p){
        System.out.println(p.name+"吃饭");
    }

    //行为-睡觉
    void sleep(Person p){
        System.out.println(p.name+"睡觉");
    }
}


//类-学生  继承自类-人
class Student extends Person{
    //成员变量
    String id;

    //无参构造
    public Student(){
        super();
        this.id = "0000";
    }

    //有参构造
    public Student(String name, int age, String id){
        super(name, age);
        this.id = id;
    }

    //设置id
    void setId(String id){
        this.id = id;
    }

    //行为-学习
    void study(Student s){
        System.out.println(s.name+"学习");
    }

    //方法-展示信息
    void show(){
        System.out.println("姓名: "+this.name);
        System.out.println("年龄: "+this.age);
        System.out.println("学号: "+this.id+"\n");
    }
}

public class ExtendsDemo {
    public static void main(String[] args){
        Student s1 = new Student();
        Student s2 = new Student("梦之空", 20, "2230502119");

        s1.show();;
        s2.show();
    }
}