java学习笔记（高琪版）----抽象类

java学习笔记（高琪版）

面向对象OOP

抽象类

抽象类必须要被继承才有意义，他的结构能给子类一个模板，限制子类的设计。

注意：
只能定义抽象方法（类也要被定义为抽象类）
only public, protected, private, static, final, transient & volatile are permitted

抽象类不能被实例化，只能定义子类
Car mycar1 = new Car(); 报错：Cannot instantiate the type Car

继承抽象类的子类必须重写父类中的抽象方法

定义Car抽象类，并且Benze和BMW为子类

package cn.lyr.oop.polymorphismAbustact;public abstract class Car {    String name;    public abstract void run();    public abstract void maxSpeed();    public void show(){        System.out.println(name);    }    public void star(){        System.out.println("启动啦！");    }}class Benze extends Car  {     public void run(){         System.out.println("run benze");     }     public void maxSpeed(){         System.out.println("maxSpeed is 290miles per hour");     }}class BMW extends Car{    public void run(){        System.out.println("run bmw");    }    public void maxSpeed(){        System.out.println("maxSpeed is 270 miles per hour");    }}

测试类

package cn.lyr.oop.polymorphismAbustact;public class test01 {    public static void main(String[]args){      //Car mycar1 = new Car();  报错：Cannot instantiate the type Car        Car mycar2 = new Benze();        mycar2.name = "京A00001";        mycar2.show();        mycar2.star();        mycar2.run();        mycar2.maxSpeed();    }}

println：
京A00001
启动啦！
run benze
maxSpeed is 290miles per hour