多态性是:

class Cup {
   int capacity
}

class TeaCup : Cup {
   string flavour
}

class CoffeeCup : Cup {
   string brand
}

Cup c = new CoffeeCup();

public int measure(Cup c) {
    return c.capacity
}

你可以只传递一个Cup而不是一个特定的实例。这在一般情况下很有帮助，因为您不必为每个cup类型提供特定的measure()实例

我正在浏览另一篇完全不同的文章。多态性出现了……现在我认为我知道多态性是什么....但显然不是用这种美丽的方式解释的。想把它写在某个地方。更好的是分享它…)

http://www.eioba.com/a/1htn/how-i-explained-rest-to-my-wife

从这部分开始阅读:

…多态性。这是一种很奇怪的说法，不同的名词可以有相同的动词。

如果有人对这些人说CUT

外科医生 发型师 这个演员

会发生什么?

外科医生开始做一个切口。 发型师会开始给某人理发。 行动者会突然停止在当前场景之外的表演， 等待导演指导。

因此，上面的表示说明了什么是OOP中的多态性(相同的名称，不同的行为)。

如果你要去参加面试，面试官要求你在我们坐在的同一个房间里讲述/展示一个多态性的生动例子，比如说-

答案-门/窗

想知道吗?

通过门/窗-人可以进来，空气可以进来，光可以进来，雨可以进来，等等。

为了更好地理解它，以一种简单的方式，我使用了上面的例子。 如果你需要代码参考，请参考上面的答案。

从理解和应用PHP多态性，感谢Steve Guidetti。

Polymorphism is a long word for a very simple concept. Polymorphism describes a pattern in object oriented programming in which classes have different functionality while sharing a common interface. The beauty of polymorphism is that the code working with the different classes does not need to know which class it is using since they’re all used the same way. A real world analogy for polymorphism is a button. Everyone knows how to use a button: you simply apply pressure to it. What a button “does,” however, depends on what it is connected to and the context in which it is used — but the result does not affect how it is used. If your boss tells you to press a button, you already have all the information needed to perform the task. In the programming world, polymorphism is used to make applications more modular and extensible. Instead of messy conditional statements describing different courses of action, you create interchangeable objects that you select based on your needs. That is the basic goal of polymorphism.

多态性是一个对象具有多种形式的能力。在OOP中，多态性最常见的用法是用父类引用引用子类对象。在这个用Java编写的例子中，我们有三种类型的车辆。我们创建了三个不同的对象，并尝试运行他们的轮子方法:

public class PolymorphismExample {

    public static abstract class Vehicle
    {
        public int wheels(){
            return 0;
        }
    }

    public static class Bike extends Vehicle
    {
        @Override
        public int wheels()
        {
            return 2;
        }
    }

    public static class Car extends Vehicle
    {
        @Override
        public int wheels()
        {
            return 4;
        }
    }

    public static class Truck extends Vehicle
    {
        @Override
        public int wheels()
        {
            return 18;
        }
    }

    public static void main(String[] args)
    {
        Vehicle bike = new Bike();
        Vehicle car = new Car();
        Vehicle truck = new Truck();

        System.out.println("Bike has "+bike.wheels()+" wheels");
        System.out.println("Car has "+car.wheels()+" wheels");
        System.out.println("Truck has "+truck.wheels()+" wheels");
    }

}

结果是:

欲了解更多信息，请访问https://github.com/m-vahidalizadeh/java_advanced/blob/master/src/files/PolymorphismExample.java。我希望这能有所帮助。

OOP中的多态性意味着一个类可以有不同的类型，继承是实现多态性的一种方式。

for example, Shape is an interface, it has Square, Circle, Diamond subtypes. now you have a Square object, you can upcasting Square to Shape automatically, because Square is a Shape. But when you try to downcasting Shape to Square, you must do explicit type casting, because you can't say Shape is Square, it could be Circle as well. so you need manually cast it with code like Square s = (Square)shape, what if the shape is Circle, you will get java.lang.ClassCastException, because Circle is not Square.