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Scala example source code file (DefaultMap.scala)

This example Scala source code file (DefaultMap.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

a, a, b, b, b1, b1, defaultmap, map, map

The Scala DefaultMap.scala source code

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



package scala.collection
package immutable

import generic._

/** A default map which implements the `+` and `-`
 *  methods of maps. It does so using the default builder for
 *  maps defined in the `Map` object.
 *  Instances that inherit from `DefaultMap[A, B]` still have to
 *  define:
 *  
 *  {{{
 *    def get(key: A): Option[B]
 *    def iterator: Iterator[(A, B)]
 *  }}}
 *  
 *  It refers back to the original map.
 *  
 *  It might also be advisable to override `foreach` or
 *  `size` if efficient implementations can be found.
 *  
 *  @tparam A    the type of the keys contained in this map.
 *  @tparam B    the type of the values associated with the keys.
 *  
 *  @since 2.8
 */
trait DefaultMap[A, +B] extends Map[A, B] { self =>

  /** A default implementation which creates a new immutable map.
   */
  override def +[B1 >: B](kv: (A, B1)): Map[A, B1] = {
    val b = Map.newBuilder[A, B1]
    b ++= this
    b += ((kv._1, kv._2))
    b.result
  }

  /** A default implementation which creates a new immutable map.
   */
  override def - (key: A): Map[A, B] = {
    val b = newBuilder
    for (kv <- this.seq ; if kv._1 != key) b += kv
    b.result
  }
}










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