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From: Lew <lewbloch@gmail.com>
Newsgroups: comp.lang.java.help
Subject: Re: Interchanging objects?
Date: Thu, 9 Feb 2012 09:21:52 -0800 (PST)
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Roedy Green wrote:
> Davej wrote, quoted or indirectly quoted someone who said :
> >I have been trying to think of a convenient way to interchange objects
> >that provide calculations that are done slightly differently. The
> >objects all have the same method names and return the same types. Is
> >there an elegant way to accomplish this? Thanks.
> 
> This is what an interface is for.  All the classes that perform the
> same operations but in a different way all implement the same
> interface.  Then you can refer to any objects of any of those classes
> by their interfacename.  What you call myinterface.calcBiggest for
> example, each object will uses its class's version of calcBiggest.
> 
> See http://mindprod.com/jgloss/interface.html

After you understand how interfaces work to encapsulate common types of 
behavior (as opposed to common implementations of behavior), you can use Java 7 
"closures" effectively. The Java version of closures is syntactic sugar for 
single-abstract-method (SAM) interfaces, that is, interfaces that define 
exactly one abstract method.

Example:

 public interface Closure
 {
   int performOp(int x, int y);
 }

The operations performed by 'performOp()' can be anything that operates on two 
'int' values and returns an 'int'.

-- 
Lew