title: Convert ListBuffer of Dataframes into one single Dataframe Spark Scala
body: <p>I have a ListBuffer of 30 DataFrames with the same fields and I want to 'append' them all at once. What is the best way and most efficient? </p>
  
  <pre><code>var result_df_list = new ListBuffer[DataFrame]()
  </code></pre>
  
  <p>I have seen that you can create a Sequence of DF like this: </p>
  
  <pre><code>val newDFs = Seq(DF1,DF2,DF3)
  newDFs.reduce(_ union _)
  </code></pre>
  
  <p>But how can you achieve this with a ListBuffer? </p>