什么是Java中的参数多态（带示例）？ [英] What is parametric polymorphism in Java (with example)?

问题描述

据我所知，参数多态是一种允许对各种数据（类型）进行统一操作的技术。我的知识是否正确？

It is my understanding that parametric polymorphism is a technique which allows uniform actions over a variety of data(types). Is my knowledge correct?

这个示例是参数多态吗？
我相信是因为Animal.talk允许调用谈话，尽管特定的动物类型（猫或狗）。

Is this example parametric polymorphism? I believe it is since Animal.talk allows talk to be called despite the specific animal type (Cat or Dog).

public interface Animal
{
  public String talk();
}

public class Cat implements Animal
{
  public String talk()
  {
    return "Cat says Meow!";
  }
}

public class Dog implements Animal
{
  public String talk()
  {
    return "Dog says Woof! Woof!";
  }
}

import java.util.*;

public class PolymorphismExample
{
  public static void main(String[] args)
  {
    Collection<Animal> animals = new ArrayList<Animal>();
    animals.add(new Cat());
    animals.add(new Dog());
    for (Animal a : animals)
    {
      System.out.println(a.talk());
    }
  }
}

问候。

编辑：如果我的例子没有具体展示参数多态性，请你提供一个？谢谢。

edit: if my example is not specifically exhibiting parametric polymorphism please would you provide one? thank you.

推荐答案

参数多态只是Java中泛型的另一个术语。这个想法很简单：你说明一个特定类将使用 types ，这个的明显例子出现在 java.util package。

"Parametric Polymorphism" is just another term for "Generics" in Java. The idea is simple: you state what types will be used by a particular class, a clear example of this is present in all the collections of the java.util package.

为了学习Java中泛型的所有细微差别，我强烈推荐Angelika Langer的常见问题解答，它探讨了规范的每个角落。

For learning all the nuances of generics in Java, I highly recommend Angelika Langer's FAQ, it explores every corner of the specification.

在您的代码中，这一行是使用泛型的一个例子： / p>

In your code, this line is an example of using generics:

Collection<Animal> animals = new ArrayList<Animal>();

指定一个集合来保存任何动物对象。

A collection is specified to hold any object that is an animal.

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