java學習筆記（高琪版）

面向物件OOP

抽象類

抽象類必須要被繼承才有意義，他的結構能給子類一個模板，限制子類的設計。

注意：
只能定義抽象方法（類也要被定義為抽象類）
only public, protected, private, static, final, transient & volatile are permitted

抽象類不能被例項化，只能定義子類
Car mycar1 = new Car(); 報錯：Cannot instantiate the type Car

繼承抽象類的子類必須重寫父類中的抽象方法

定義Car抽象類，並且Benze和BMW為子類

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("啟動啦！");
    }
}


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"
 
);
    }
}

測試類

package cn.lyr.oop.polymorphismAbustact;

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

    }


}

println：
京A00001
啟動啦！
run benze
maxSpeed is 290miles per hour