toString mkString
mkStringを使いましょう。
final class StringBuilder(private val underlying: JavaStringBuilder) ... /** Returns a new String representing the data in this sequence. * * @note because toString is inherited from AnyRef and used for * many purposes, it is better practice to call mkString * to obtain a StringBuilder result. * @return the current contents of this sequence as a String */ override def toString = underlying.toString /** Returns a new String representing the data in this sequence. * * @return the current contents of this sequence as a String */ override def mkString = toString
Google翻訳さま「toStringはAnyRefから継承され、多くの目的に使用されるため、mkStringを呼び出してStringBuilderの結果を取得することをお勧めします。」