title: How to create TimestampType column in spark from string
body: <p>I have some datas contained in an Array of String like below (just for exemple): </p>
  
  <pre><code>val myArray = Array("1499955986039", "1499955986051", "1499955986122")
  </code></pre>
  
  <p>I want to map my list to an array of Timestamp, in order to create an RDD (myRdd) then create a dataframe like this</p>
  
  <pre><code>val df = createdataframe(myRdd, StructType(StructField("myTymeStamp", TimestampType,true)
  </code></pre>
  
  <p>My question is not how to create the Rdd, but how to replace string by millisecond timestamp. Do you have any idea? Thanks</p>