多态

多态：对象执行某个行为方法式表现出不同的形态。
多态分两种：静态多态（编译多态）通过方法重载来实现，动态多态（运行多态），通过重写来实现。

动态多态一般通过父类的引用，指向子类的实例来实现。实例调用的时候，调的是子类的方法。

练习：

public class Che {        //父类Che
    protected String cheming;
    private String leixing;
    private String dangwei;
    
    public Che(String cheming){        //重载  参数符合会运行
        this.cheming = cheming;
    }
    public Che(String cheming,String leixing,String dangwei){  //重载  参数符合会运行
        this.cheming = cheming;
        this.leixing = leixing;
        this.dangwei = dangwei;
        
    }
    public void shache(){
        System.out.println(cheming+"z");
    }
    public void jiasu(){
        System.out.println(cheming+"s");
    }
    public void qidong(){
        System.out.println(cheming+"h");
    }
}

public class Byd extends Che {       //子类继承Che
    public Byd(String cheming){
        super(cheming);
    }
    public Byd(String cheming,String leixing,String dangwei){
        super(cheming,leixing,leixing);        
    }
    public void shache(){
        System.out.println(cheming+"正在刹车"+"1");
    }
    public void jiasu(){
        System.out.println(cheming+"正在加速"+"1");
    }
    public void qidong(){
        System.out.println(cheming+"正在启动"+"1");
    }
    
}

public class Jipu extends Che {      //子类也是继承Che
    public Jipu(String cheming) {  
        super(cheming);
    }
    public Jipu(String cheming,String leixing,String dangwei){  
        super(cheming,leixing,dangwei);
    }
    
    public void qidong(){
        System.out.println(cheming+"正在启动"+"2");
    }
    
    public void jiasu(){
        System.out.println(cheming+"加速"+"2");
    }
    
    public void shache(){
        System.out.println(cheming+"正在刹车"+"2");
    }
}

public class Siji {               //定义一个类Siji方法来调用父类方法
    public void jiashi(Che c){   //引用父类Che实例化子类
        c.qidong();              
        c.jiasu();
        c.shache();    
    }
}

    public static void main(String[] args) {
        Che b = new Byd("比亚迪");    //实参
        Che j = new Jipu("吉普");    //实参
        Siji s = new Siji();

        s.jiashi(b);     //再用jiashi()方法调用Byd
 
        s.jiashi(j);    //再用jiashi()方法调用Jipu  实现运行多态（动态多态）
    }
}