object Test extends Application { val str = "ABCDEFGHIJKLMABCDEFGHIJKLM" type SB = { def indexOf(str: String): Int def indexOf(str: String, fromIndex: Int): Int def lastIndexOf(str: String): Int def lastIndexOf(str: String, fromIndex: Int): Int } import scala.collection.mutable.{ StringBuilder => ScalaStringBuilder } import java.lang.{ StringBuilder => JavaStringBuilder } val sbScala = new ScalaStringBuilder() append str val sbJava = new JavaStringBuilder() append str val sbs: List[SB] = List[SB](sbScala, sbJava) def sameAnswers(f: (SB) => Int) = assert(f(sbScala) == f(sbJava)) sameAnswers(_.indexOf("")) sameAnswers(_.indexOf("G")) sameAnswers(_.indexOf("ABC")) sameAnswers(_.indexOf("KLM")) sameAnswers(_.indexOf("QZV")) sameAnswers(_.indexOf("LMABC")) sameAnswers(_.lastIndexOf("")) sameAnswers(_.lastIndexOf("M")) sameAnswers(_.lastIndexOf("ABCDEFG")) sameAnswers(_.lastIndexOf("KLM")) sameAnswers(_.lastIndexOf("QZV")) sameAnswers(_.lastIndexOf("GHI", 22)) sameAnswers(_.lastIndexOf("KLM", 22)) }