java学习笔记----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