继承

下面的类是Human的父类，拥有两个属性和两个获取接口。

package com.yuque.phil616.oop.extend;
public class Human {
    String name;
    int age;
    /*
    * Every human have a name.
    * Every human have an age.
    * students and teachers are human.
    * however their own properties are not common.
    * we can know more at https://www.runoob.com/java/java-inheritance.html
    * */
    public int getAge() {
        return age;
    }
    public String getName() {
        return name;
    }
}

下面的Student类继承了Human类，因为学生是人类的子类，人类拥有的两个属性：姓名和年龄学生也有，而学生拥有的两个属性：学号和班级并不是所有人类都有的，因此学生类继承了人类，保留了人类的属性和方法，同时也增加了自己的属性。

package com.yuque.phil616.oop.extend;
public class Student extends Human{
    int studentNumber;
    int classNumber;
    /*
    * a student is a human, so it has name and age;
    * however, as a student, it should have student number and classes number
    * this is extend
    * */
    @Override
    public int getAge() {
        return super.getAge();
    }
    @Override
    public String getName() {
        return super.getName();
    }
    public int getClassNumber() {
        return classNumber;
    }
    public int getStudentNumber() {
        return studentNumber;
    }
}

同理下面的Teacher类也有人类的属性，也有属于自己的属性。

package com.yuque.phil616.oop.extend;
public class Teacher extends Human{
    String department;
    int salary;
    /*
    * teacher is a human,but not all the human have salary and department name;
    * */
    @Override
    public String getName() {
        return super.getName();
    }
    @Override
    public int getAge() {
        return super.getAge();
    }
    public int getSalary() {
        return salary;
    }
    public String getDepartment() {
        return department;
    }
}