Trimming a string at a certain number of bytes

TrimString.scala

import java.nio.{ByteBuffer, CharBuffer}
import java.nio.charset.Charset

def trimAtBytes(str: String, len: Int, charset: Charset) = {
  val outBuf = ByteBuffer.wrap(new Array[Byte](len))
  val inBuf = CharBuffer.wrap(str.toCharArray())
  charset.newEncoder().encode(inBuf, outBuf, true)
  new String(outBuf.array, 0, outBuf.position(), charset)
}

val multiByteStr = "これはどのように切り捨てられてしまいます？"
val singleByteStr = "Will this work?"

trimAtBytes(multiByteStr, 10, Charset.forName("UTF-8"))
trimAtBytes(singleByteStr, 10, Charset.forName("UTF-8"))