Linked by Bjorn Raupach on Thu 17th Jul 2008 06:01 UTC
Java Today was one of those days when I wished Java would support multiple return values. I had to develop a rather CPU-intensive algorithm which would compute a solution for a knotty constraint problem. Having a solution alone is sometimes not enough and you also need to add some parameters which measure the quality of the computed outcome. Most of these accompanying parameters can or have to be computed within the algorithm itself, but Java allows you to return only one value either an object or a primitive type. People working with Lisp, MATLAB or Perl, just to mention a few, don't have a problem like this at all. Functions supporting multiple return values is already implemented at the language level and frameworks make heavy use of this. But as a Java programmer you are pretty much stuck here and need to consider some other means to come out of this situation. In the following I would like to give some hints on that topic. Hopefully they are of help for anyone having the same problem every now and then.
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The Scala way
by John Nilsson on Sat 19th Jul 2008 13:40 UTC
John Nilsson
Member since:
2005-07-06

Scala solves this in a manner that actually preserves the nice design principle.

Here's an example:

object MultipleReturnValues extends Application {

// Define a class for the return value
case class RetVal(intPart: Int, fracPart: Double)

// Define a function returning values of that type
def floor(value: Double) : RetVal = new RetVal(value.floor.toInt, value - value.floor)

// Extract the parts of the return value and declare vals to hold them
val RetVal(i,f) = floor(10.4)

// Print the result
Console.println(i + " " + f)
}

The nice thing with scala is that it can easily be mixed with Java code.

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