title: Spark: show dataframe content in logging (Java)
body: <p>I want to know how to show dataframe content (rows) in Java ?
  I tried using <code>log.info(df.showString())</code>, but it prints unreadable characters. I want to use <code>df.collectAsList()</code> but I have to do filter afterwards so I can't do this.</p>
  
  <p>Thank you.</p>