多态性的好处 [英] Benefit of Polymorphism

问题描述

当我开始寻找多态性的好处时，我在这里找到这个问题。但在这里我无法找到答案。让我告诉我想要找到什么。这里我有一些课程：

  class CoolingMachines {
 public void startMachine（）{
 //否执行
} 
 public void stopMachine（）{
 //无执行
} 
} 
 
类冰箱扩展CoolingMachines {
 public void startMachine（）{
 System.out.println（Refrigerator Starts）; 
} 
 public void stopMachine（）{
 System.out.println（Refrigerator Stop）; 
} 
 public void trip（）{
 System.out.println（Refrigerator Trip）; 
} 
} 
 
类AirConditioner扩展CoolingMachines {
 public void startMachine（）{
 System.out.println（AC Starts）; 
} 
 public void stopMachine（）{
 System.out.println（AC Stop）; 
} 
} 
 
公共类PolymorphismDemo {
 CoolingMachines cm = new Refrigerator（）; 
冰箱rf =新冰箱（）; 
} 
  

现在我在Demo类中创建了两个对象，并引用了冰箱。我完全理解，从 rf 对象，我可以调用 trip（）方法c> Refrigerator ，但该方法将隐藏在 cm 对象中。现在我的问题是为什么我应该使用多态或我为什么要使用

  CoolingMachines cm = new Refrigerator（）;我b 
 
 $ b $ $ p> 冰箱rf =新冰箱（）; 
  

多态对象的效率是好还是重量轻？这两个对象的基本目的和区别是什么？ cm.start（）; 和 rf.start（）？

$ b之间有什么区别吗？ $ b

解决方案

处理清单时很有用...
一个简短的例子：

 列表与LT; CoolingMachines> coolingMachines = ... //一个CoolingMachines列表
 for（CoolingMachine current：coolingMachines）{
 current.start（）; 
} 
  

或者当你想允许方法使用<$的任何子类时c $ c> CoolingMachines

When I started to look for the benefits of polymorphism, I found with this question here. But here I was unable to find my answer. Let me tell what I want to find. Here I have some classes:

class CoolingMachines{
    public void startMachine(){
        //No implementationion
    }
    public void stopMachine(){
        //No implementationion
    }
}

class Refrigerator extends CoolingMachines{
    public void startMachine(){
        System.out.println("Refrigerator Starts");
    }
    public void stopMachine(){
        System.out.println("Refrigerator Stop");
    }
    public void trip(){
        System.out.println("Refrigerator Trip");
    }
}

class AirConditioner extends CoolingMachines{
    public void startMachine(){
        System.out.println("AC Starts");
    }
    public void stopMachine(){
        System.out.println("AC Stop");
    }
}

public class PolymorphismDemo {
    CoolingMachines cm = new Refrigerator();
    Refrigerator rf = new Refrigerator();
}

Now here I created two objects in the Demo class and are references of Refrigerator. I have completely understood that from the rf object I am able to call the trip() method of Refrigerator, but that method will be hidden for the cm object. Now my question is why should I use polymorphism or why should I use

CoolingMachines cm = new Refrigerator();

when I am OK with

Refrigerator rf = new Refrigerator();

Is polymorphic object's efficiency is good or light in weight? What is the basic purpose and difference between both of these objects? Is there any difference between cm.start(); and rf.start()?

解决方案

It is useful when you handle lists... A short example:

List<CoolingMachines> coolingMachines = ... // a list of CoolingMachines 
for (CoolingMachine current : coolingMachines) {
    current.start();
}

Or when you want to allow a method to work with any subclass of CoolingMachines

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