CODEWITHSUNDEEP
scala
Hartmut Pfarr
Hartmut Pfarr

Reputation: 6139

Return first element of array, in a def

Can you please help me understand, why the second def is not compiling, and how to write the second def for that it is compiling (return first entry of Array in one line). Thanks!

import java.awt.{GraphicsDevice, GraphicsEnvironment}

class SeparatedTestCase {

   def does_compile: GraphicsDevice = {
      val ge: GraphicsEnvironment = GraphicsEnvironment.getLocalGraphicsEnvironment
      val devices: Array[GraphicsDevice] = ge.getScreenDevices
      devices(0)
   }

   def does_not_compile: GraphicsDevice = {
      val ge: GraphicsEnvironment = GraphicsEnvironment.getLocalGraphicsEnvironment
      val device0: GraphicsDevice = (ge.getScreenDevices)(0)   // <---- compile error
      device0
   }
}

//Error:(13, 59) no arguments allowed for nullary method getScreenDevices: ()Array[java.awt.GraphicsDevice]
//val device0: GraphicsDevice = (ge.getScreenDevices)(0)

Upvotes: 1

Views: 47

Answers (1)

Vladimir Matveev
Vladimir Matveev

Reputation: 127741

You have to invoke the method with explicit parentheses:

ge.getScreenDevices()(0)

This does not compile, because your second invocation means the same as

ge.getScreenDevices(0)

which does not do what you want because getScreenDevices is a Java null-ary method which can be invoked either with parentheses or not, and if you specify one set of parentheses, Scala assumes that you want to invoke this method with these parameters, which of course won't work since it does not accept any arguments.

Upvotes: 3

Related Questions