Scala example source code file (StringOps.scala)

This example Scala source code file (StringOps.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, char, int, int, list, list, none, option, option, seq, some, string, string, stringops

The Scala StringOps.scala source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2002-2011, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */


package scala.tools
package util

/** This object provides utility methods to extract elements
 *  from Strings.
 *
 *  @author Martin Odersky
 *  @version 1.0
 */
trait StringOps {
  def onull(s: String)                    = if (s == null) "" else s
  def oempty(xs: String*)                 = xs filterNot (x => x == null || x == "")
  def ojoin(xs: Seq[String], sep: String) = oempty(xs: _*) mkString sep
  def ojoinOr(xs: Seq[String], sep: String, orElse: String) = {
    val ys = oempty(xs: _*)
    if (ys.isEmpty) orElse else ys mkString sep
  }
  
  def decompose(str: String, sep: Char): List[String] = {
    def ws(start: Int): List[String] =
      if (start == str.length) List()
      else if (str.charAt(start) == sep) ws(start + 1)
      else {
        val end = str.indexOf(sep, start)
        if (end < 0) List(str.substring(start))
        else str.substring(start, end) :: ws(end + 1)
      }
    ws(0)
  }

  def words(str: String): List[String] = decompose(str, ' ')
  
  def stripPrefixOpt(str: String, prefix: String): Option[String] = 
    if (str startsWith prefix) Some(str drop prefix.length)
    else None
    
  def stripSuffixOpt(str: String, suffix: String): Option[String] =
    if (str endsWith suffix) Some(str dropRight suffix.length)
    else None
  
  def splitWhere(str: String, f: Char => Boolean, doDropIndex: Boolean = false): Option[(String, String)] =
    splitAt(str, str indexWhere f, doDropIndex)

  def splitAt(str: String, idx: Int, doDropIndex: Boolean = false): Option[(String, String)] =
    if (idx == -1) None
    else Some(str take idx, str drop (if (doDropIndex) idx + 1 else idx))
  
  /** Returns a string meaning "n elements".
   *
   *  @param n        ...
   *  @param elements ...
   *  @return         ...
   */
  def countElementsAsString(n: Int, elements: String): String =
    n match {
      case 0 => "no "    + elements + "s"
      case 1 => "one "   + elements
      case 2 => "two "   + elements + "s"
      case 3 => "three " + elements + "s"
      case 4 => "four "  + elements + "s"
      case _ => "" + n + " " + elements + "s"
    }
    
  /** Turns a count into a friendly English description if n<=4. 
   *
   *  @param n        ...
   *  @return         ...
   */
  def countAsString(n: Int): String =
    n match {
      case 0 => "none"
      case 1 => "one"
      case 2 => "two"
      case 3 => "three"
      case 4 => "four"
      case _ => "" + n 
    }    
}

object StringOps extends StringOps { }