What I learned on Scala: * Traits with a same private var name does not conflict. * Traits with a same method name do conflict.

gistfile1.scala

/**
 * Traits with a same private var name does not conflict.
 * Traits with a same method name do conflict.
 */

trait Countable {
  private var _count:Int = 0
  def count:Int = _count
  def countup:Unit = _count += 1
}

trait Sizable {
  private var _count:Int = 0
  def size:Int = _count
  def sizeup:Unit = _count += 1
  // def count:Int = size // uncomment this and you get the error below:
  /**
   * error: overriding method count in trait Countable of type => Int;
   *  method count in trait Sizable of type => Int needs `override' modifier
   *  val container = new Container with Countable with Sizable
   *                      ^
   */

}

class Container {
}

val container = new Container with Countable with Sizable
println("before: countainer.countup")
println("countainer.count = " + container.count)
println("countainer.size = " + container.size)
container.countup
println("after: countainer.countup")
println("countainer.count = " + container.count)
println("countainer.size = " + container.size)

/**
 * result:
 * before: countainer.countup
 * countainer.count = 0
 * countainer.size = 0
 * after: countainer.countup
 * countainer.count = 1
 * countainer.size = 0
 */