Scala example source code file (Null.scala)

This example Scala source code file (Null.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

boolean, illegalargumentexception, int, metadata, metadata, namespacebinding, namespacebinding, node, seq, string, string, stringbuilder, stringbuilder, topscope

The Scala Null.scala source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2011, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */



package scala.xml

import Utility.{ isNameStart }
import scala.collection.Iterator

/** Essentially, every method in here is a dummy, returning Zero[T].
 *  It provides a backstop for the unusual collection defined by MetaData,
 *  sort of a linked list of tails.
 */
case object Null extends MetaData {    
  override def iterator = Iterator.empty
  override def append(m: MetaData, scope: NamespaceBinding = TopScope): MetaData = m
  override def filter(f: MetaData => Boolean): MetaData = this

  def copy(next: MetaData) = next
  def getNamespace(owner: Node) = null

  override def hasNext = false
  def next = null
  def key = null
  def value = null
  def isPrefixed = false

  override def length = 0
  override def length(i: Int) = i
  
  override def strict_==(other: Equality) = other match {
    case x: MetaData  => x.length == 0
    case _            => false
  }
  override def basisForHashCode: Seq[Any] = Nil

  def apply(namespace: String, scope: NamespaceBinding, key: String) = null
  def apply(key: String) = {
    if (!isNameStart(key.head))
      throw new IllegalArgumentException("not a valid attribute name '"+key+"', so can never match !")
      
    null
  }

  def toString1(sb: StringBuilder) = ()
  override def toString1(): String = ""
  override def toString(): String = ""

  override def buildString(sb: StringBuilder): StringBuilder = sb
  override def wellformed(scope: NamespaceBinding) = true

  def remove(key: String) = this
  def remove(namespace: String, scope: NamespaceBinding, key: String) = this
}