title: Any example of Apache Spark org.apache.spark.sql.DataFrameNaFunctions usage? ..drop() doesn't seem to work?
body: <p>I am trying to filter a dataset with NA values..found  org.apache.spark.sql.DataFrameNaFunctions 
  but it seems its drop() or drop("any") doesn't seem to work properly..anyone tried ..or please share usage in java ..thank you...</p>
  
  <pre><code>    import org.apache.spark.sql.DataFrameNaFunctions;
      Dataset&lt;Row&gt; inputDS=spark.read().option("header","true").
                                   csv("inputfile.csv");
      inputDS.show();
  
      //Updated dataset...remove null or NAN 
      DataFrameNaFunctions inputDatasetsansNullorNAN=new DataFrameNaFunctions(inputDS);
      Dataset&lt;Row&gt; inputDSnulldropped=inputDatasetsansNullorNAN.drop();
      inputDSnulldropped.show();
  </code></pre>
  
  <p>............
  Input File </p>
  
  <pre><code>name item
  </code></pre>
  
  <p>1.Alice,milk
   2. Bob,null 
   3. NA,<br>
   4. Test,a
   5. NA,NA
   6. null,NA
   7. Bob, NA
   8. 
   9. </p>
  
  <h1>output</h1>
  
  <p>name item
  1.Alice milk
  2.Bob null
  3.Test a
  4.NA NA
  5.null NA
  6.Bob NA</p>