What's an example of duck typing in Java?

Question

I just recently heard of duck typing and I read the Wikipedia article about it, but I'm having a hard time translating the examples into Java, which would really help my understanding.

Would anyone be able to give a clear example of duck typing in Java and how I might possibly use it?

Answer 1

Java is by design not fit for duck typing. The way you might choose to do it is reflection:

public void doSomething(Object obj) throws Exception {      obj.getClass().getMethod("getName", new Class<?>[] {}).invoke(obj); } 

But I would advocate doing it in a dynamic language, such as Groovy, where it makes more sense:

class Duck {     quack() { println "I am a Duck" } }  class Frog {     quack() { println "I am a Frog" } }  quackers = [ new Duck(), new Frog() ] for (q in quackers) {     q.quack() } 

Reference

Answer 2

See this blog post. It gives a very detailed account of how to use dynamic proxies to implement duck typing in Java.

In summary:

• create an interface that represents the methods you want to use via duck typing
• create a dynamic proxy that uses this interface and an implementation object that invokes methods of the interface on the underlying object by reflection (assuming the signatures match)