向上转型实例

myMonitor.java

interface monitor{
    public void displayText();
    public void displayGraphics();
}   //定义监视器接口
-----------------------------------------------------
class LCD implements monitor{
    public void displayText(){
        System.out.println("this is the lcd screen");
    }
    
    public void displayGraphics(){
        System.out.println("nice");
    }
    
}   //实现接口
-----------------------------------------------------
class IPS implements monitor{
      public void displayText(){
        System.out.println("this is the ips screen");
    }
    
    public void displayGraphics(){
        System.out.println("great");
    }
    
}
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public class myMonitor{
    public static void main(String[] args){
        run(new LCD);
        run(new IPS);
    }
    
    public static void run(monitor m){
        m.displayText();
        m.displayGraphics();
    }   //这里的monitor并不是实例化，而是生成一个引用，在语法上是可以的，而后在参数里生成一个子接口以达到向上转型
}